AUdIoCoUrSeS
Joined: 31 Oct 2002
Posts: 2014
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| Week 10 - Synchronisation |
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Have fun, with this last topic, after which we then start to summarise and start to clear up anything we have missed.
Yo'll note there are not many here, so please use them for creating more dialogue between you all this time.
1. Explain why it is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
4. Describe THREE major operational advantages of having two modular digital multitrack recorders such as the ADAT or DTRS formats over a format which records sixteen tracks on the same tape on a single machine.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output
b) why the `sync' output is required when overdubbing.
7. It is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously. Why is this?
8. Some hard disk recording systems have mixing facilities so that several tracks can be mixed into a stereo output. If no other outputs are available why must the system incorporate reverb internally?
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?
c) If MIDI Machine Control (MMC) is not used, describe briefly the two distinct stages of operation when recording a piece of sequenced music to multitrack tape.
d) What is the advantage of MMC?
e) In a system using MMC, while playback or recording progresses the multitrack and sequencer will be running in sync. At this moment which is master and which is slave?
11. You have been given an unlabelled tape to play which starts with a warbling tone. What noise reduction system might have been used?
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?
c) Name three domestic noise reduction systems invented by the Dolby company.
d) Give the name of another fairly common analogue noise reduction system.
e) Where would you find the ATRAC digital noise reduction system?
12. When recording onto analogue or digital multitrack tape, in a situation where synchronisation is going to be used, what procedure must be carried out before any recording can begin?
b) Your studio manager has given you a multitrack tape containing music and timecode to copy. What must you do to ensure that the timecode is copied correctly?
c) A multitrack tape of a band with no sequenced instruments was striped with timecode at the start of the session and has subsequently been edited? Would it be good practice to use the existing timecode as a synchronisation reference for the console automation system during the mix?
d) Referring to c) above, why would it not be a problem to re-stripe the tape with timecode and erase the original timecode, even if the generator does not have a jam sync function?
e) You have striped timecode on track 24 of an analogue tape and recorded a bass guitar on track 23. When you try and synchronise a MIDI sequencer using a cheap timecode to MTC convertor, the sequencer often stops or loses sync. Why?
13. When working with MIDI and multitrack tape, does the multitrack recorder synchronise to the sequencer or does the sequencer synchronise to the multitrack tape?
b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with timecode to synchronise a sequencer?
c) Imagine that several tracks of a MIDI sequence have been transferred to multitrack tape. The producer decides that he wants to varispeed the tape a little faster. Should this be done before or after the remaining sequencer tracks have been transferred to tape? Explain your answer.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
15. You have been asked to remix a song (in the sense of creating a completely new version) originally made on multitrack tape in the early 1970s.
a) What would be the main problem in synchronising a sequencer to the original tape?
b) If you decided only to use the vocal track from the original recording, how would you make the lines fit in time with your new MIDI sequencer arrangement?
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
d) The record company decides that it wants to keep a lot of the original instrumentation, but also likes your strict tempo MIDI sequence. What type of equipment should you use to put everything together?
16. You are working with a multitrack recorder that will slave to SMPTE/EBU timecode from (for instance) a video machine, but has no other means by which it may be externally controlled. Imagine you stop the master machine, rewind the tape to the beginning and start playing. What will the multitrack do?
_________________
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Mon Nov 03, 2003 5:03 pm |
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mommi
Joined: 21 Apr 2003
Posts: 47
Location: Tallinn, Estonia |
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Hi. As I started to construct my answers, it became apparent I don't feel particularly strong in these topics (syncing and noise reduction). So I decided to throw out the first part of my effort for your criticism and suggestions. 
1. Explain why it is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously.
This allows to record alternative takes and later choose the best one for playback/mixing.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
Because playing at faster speed involves greater data retrieval rates. How fast data can be read/transferred from a disk has a major effect on how many tracks can be played simultaneously.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
- Much greater flexibility in editing. Copying, pasting, moving, deleting are just a matter of menu functions, with undo available. Digital tapes are hard to edit.
- Any part of the material can be accessed quickly, as opposed to a tape where all access is linear and requires winding.
4. Describe THREE major operational advantages of having two modular digital multitrack recorders such as the ADAT or DTRS formats over a format which records sixteen tracks on the same tape on a single machine.
- Having two separate machines allows for copying between tapes. This adds some editing power. E.g., you could record a part of a track from one cassette to another, and use that copy for moving the passage to another place on the first cassette.
- You can duplicate cassettes.
- Alternative takes could be recorded on different tapes. E.g. record the basic tracks on one cassette and use several others for alternative takes of overdubs.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder.
The operations on a hard disk recorder are non-destructive. If, after recording over a section of a previous material, you find the punch in was misplaced and destroyed some of your good take, it is simply a matter of choosing undo from a menu to roll back to the previous state. On a tape recorder, once new data has been recorded, there is no way to get the old data back.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output
b) why the `sync' output is required when overdubbing.
a) On analogue recording, separate heads are used for recording and playback. Although having different characteristics, the two heads are similar in nature and so you could use a recording head for playback. Sync output means the the recording head is used for playback.
b) Sync output is necessary when overdubbing because it takes time for a tape to travel from the recording head to the playback one. If foldback signals were taken from the playback head, an overdubbing artist would have no chance to perform in time with the prerecorded tracks.
7. It is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously. Why is this?
It is to allow for recording several takes of the same material. Later, only the best take is chosen and played back, the others are ignored.
8. Some hard disk recording systems have mixing facilities so that several tracks can be mixed into a stereo output. If no other outputs are available why must the system incorporate reverb internally?
Since there are no other outputs at all, the only sensible way to use that system is to mix the tracks down, send the mix out from the stereo output and record it. It is normal to apply different amount of reverberation to different tracks but, at this case, there are no auxiliary outputs for feeding an external reverb unit. So the internal reverb has to be used.
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
Greater flexibility in editing and greater speed in locating any part of the material. (See q. 3 above.)
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
- If to begin at the head of the tune, FSK can be used to synchronize the playback of a sequencer and tape recording. This method requires no additional equipment, but is of very limited capabilities.
- A much more advanced method is to use SMPTE or MTC. Then a SMPTE Time Code generator must be used to record the Time Code onto a track (usually the highest number) of the multitrack tape machine. If the sequencer is not capable of reading SMPTE time code, it will respond to MTC (MIDI Time Code).
- In the latter case (sequencer wanting MTC), a SMPTE to MTC converter must be used. Chances are that the multitrack recorder contains it, otherwise an external converter is necessary.
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?
As of now, I would think because that way you can synchronize them. While two MIDI devices can run in sync via MIDI clocks and SPPs, for me it seems there is no way to record MIDI clock data onto tape. Or is there?
c) If MIDI Machine Control (MMC) is not used, describe briefly the two distinct stages of operation when recording a piece of sequenced music to multitrack tape.
- Stripe a track of a multitrack recorder with a SMPTE time code. Hook the track's output into the sequencer's external sync input (via a SMPTE to MTC converter if necessary). Set the sequencer to synchronize to the external input, indicating an offset time - the time the sequencer will start playback.
- Initiate recording on the multitrack, while the time code track in playback mode. Now the sequencer will chase the multitrack.
d) What is the advantage of MMC?
MIDI Machine Control (MMC) is a protocol specifically designed to remotely control hard disk recording systems, and other machines used for record or playback. MMC gives remote access to the basic transport functions like Start, Stop, Fast-Forward and other 'tape-like' controls. Two or more MIDI devices can be operated centrally by means of MMC. Still, MMC is not a synchronizing signal - MIDI Clock, MTC or SMPTE must be used for synchronizing the devices.
e) In a system using MMC, while playback or recording progresses the multitrack and sequencer will be running in sync. At this moment which is master and which is slave?
I suppose the multitrack would still be the time code master. Which one would be the transport master is probably a matter of preferences, i.e. what equipment do you like to use as an operation centre. |
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Tue Nov 04, 2003 8:16 am |
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mommi
Joined: 21 Apr 2003
Posts: 47
Location: Tallinn, Estonia |
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Alright, here's my another effort. Will be interesting to see what you guys think of these topics. 
11. You have been given an unlabelled tape to play which starts with a warbling tone. What noise reduction system might have been used?
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?
Nothing at all, seems. Or maybe DBX, with the playing machine not capable of decoding it. DBX uses compression in an encoding stage. Compression, as we know, raises the level of noise amongst others. During playback this sould be expanded back, which would lower the noise level.
c) Name three domestic noise reduction systems invented by the Dolby company.
- Dolby B, the first one to be used in domestic equipment. Operates on frequencies starting from 400 Hz, giving up to 10 dB reduction in tape hiss.
- Dolby C, a more advanced and expensive system. Goes down to 100 Hz and uses anti-saturation circuitry to prevent HF overload in signals that already have a high level of HF content. Up to 20 dB of noise reduction.
- Dolby S, resembling Dolby C with some of the filter technology from Dolby SR (a very effective and expensive professional noise reduction system).
d) Give the name of another fairly common analogue noise reduction system.
DBX. It applies high frequency pre-emphasis in addition to compressing over the whole frequency range before recording. The idea is compress the dynamic range down for recording (so the signal levels fit into what the tape can represent) and expand it later during playback along with de-emphasis. That approach (compressing and expanding) is called companding.
e) Where would you find the ATRAC digital noise reduction system?
http://www.minidisc.org/aes_atrac.html
In Minidisks. ATRAC (Adaptive Transform Acoustic Coding) is an audio coding system developed by Sony. IT is based on psychoacoustic principles, taking into account sensitivity of the human ear and masking phenomena. ATRAC compresses audio to approximately 1/5 of the original data rate with virtually no loss in sound quality.
12. When recording onto analogue or digital multitrack tape, in a situation where synchronisation is going to be used, what procedure must be carried out before any recording can begin?
In order to use synchronisation, the tape must first be striped with SMPTE timecode. After that, the multitrack can be used as a timecode master allowing to run other equipment in sync with it.
b) Your studio manager has given you a multitrack tape containing music and timecode to copy. What must you do to ensure that the timecode is copied correctly?
Regenerate it by means of a timecode generator, capable of 'jam 'syncing' (taking in a timecode and regenerating it).
c) A multitrack tape of a band with no sequenced instruments was striped with timecode at the start of the session and has subsequently been edited? Would it be good practice to use the existing timecode as a synchronisation reference for the console automation system during the mix?
I suppose not. Not sure how the console would handle sudden jumps in time(code), probably it just could not read it anymore. Re-striping the tape with new timecode seems to be a more appropriate option. At least it is easier to follow the position of tape (song) then.
d) Referring to c) above, why would it not be a problem to re-stripe the tape with timecode and erase the original timecode, even if the generator does not have a jam sync function?
A jam sync function is the ability of a timecode generator to regenerate new timecode in sync with the incoming signal. Since we have no sequenced instruments, erasing the original and bringing in a new timecode does not affect any external equipment.
e) You have striped timecode on track 24 of an analogue tape and recorded a bass guitar on track 23. When you try and synchronise a MIDI sequencer using a cheap timecode to MTC convertor, the sequencer often stops or loses sync. Why?
The signal from the bass guitar track crosstalks into the timecode track. This interferes with the convertor's ability to read and understand timecode.
13. When working with MIDI and multitrack tape, does the multitrack recorder synchronise to the sequencer or does the sequencer synchronise to the multitrack tape?
The sequencer synchronises to the multitrack tape. There has to be timecode recorded onto one track of the multitrack.
b) When working with an ADAT recorder, why wouldn't you necessarily have to stripe the tape with timecode to synchronise a sequencer?
Because ADATs can generate and send out the timecode themselves.
c) Imagine that several tracks of a MIDI sequence have been transferred to multitrack tape. The producer decides that he wants to varispeed the tape a little faster. Should this be done before or after the remaining sequencer tracks have been transferred to tape? Explain your answer.
This should be done after all the sequencer tracks have been transferred. Changing the tape speed changes the playback pitch, while with MIDI sound production this is not the case. Since some of the tracks were already recorded on tape, changing the tape speed for the rest of the recording process would result in tuning differences between tracks already on tape and the ones being recorded.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
Because those systems adapt themselves to the signal characteristics. For example, there is less need for noise reduction when the signal level is high, since high level signals mask the noise anyway. Dolby noise reduction systems act only on signals not having high enough level near the frequency region of noise.
15. You have been asked to remix a song (in the sense of creating a completely new version) originally made on multitrack tape in the early 1970s.
a) What would be the main problem in synchronising a sequencer to the original tape?
Probably the performance on the tape is not of very strict tempo. Sequencers, on the other hand, keep stable tempo if not programmed otherwise. Getting the two together could be problematic.
b) If you decided only to use the vocal track from the original recording, how would you make the lines fit in time with your new MIDI sequencer arrangement?
If tempo was kept stable during the song, it would be no problem to find out what is was. So the sequencer would play in that tempo. To account for slight timing differences, I think I would go digital there and divide the vocal into manageable pieces of say one/two or more bars long. Assign these samples to different notes on a sequencer and trigger them on appropriate places.
Or import the vocal track into a sequencer as it was and make adjustments to the MIDI arrangement's timing, referencing to the vocal track's graphical representation.
Or maybe even use an audio sequencer, putting timing cues on necessary places? This, of course, makes unjustice to the original, since we are forcing it to follow our new arrangement, not on the contrary ...
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
1) Try 15% pitch shifting (to lower it). Playing audio faster will raise the frequencies. If the multitrack has a varispeed control, use it.
2) Maybe again use an audio sequencer This allows you to insert timing cues (so called warp marks) on a track and, when you choose to play your piece on another tempo, it will use these marks to speed things up without affecting the pitch.
d) The record company decides that it wants to keep a lot of the original instrumentation, but also likes your strict tempo MIDI sequence. What type of equipment should you use to put everything together?
A MIDI / audio sequencer. Import some of the original tracks (eg the drums or bass) into the sequencer and align (program) the MIDI arrangement so it takes into account timing changes in the original. After that, use common synchronization techniques to mix the song down, playing the multitrack and the sequencer in sync.
16. You are working with a multitrack recorder that will slave to SMPTE/EBU timecode from (for instance) a video machine, but has no other means by which it may be externally controlled. Imagine you stop the master machine, rewind the tape to the beginning and start playing. What will the multitrack do?
I suppose it will stop together with the master, since it receives no timecode then. Afterwards, when the master starts over from the beginning, the multitrack will receive timecode and continue from where it was stopped earlier. |
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Wed Nov 05, 2003 11:03 am |
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Albow
Joined: 02 Sep 2003
Posts: 27
Location: Spain |
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Ok. Mommi,
I haven't read through your answers yet, but here are my efforts to compare them with
1. Explain why it is common for a multitrack hard disk recording system to
be able to store more tracks in synchronisation than it can play
simultaneously.
To try things out, you may choose to store any number of tracks to be played
together, without wanting to ever play them all together at the same time.
They have to all be in sync so that each selected track can be played
together with another.
2. Explain why some multitrack hard disk recording systems can play back
much slower than normal speed, but only a little faster.
It is easier to slow down the speed of the disk, because the mechanical parts
of the disk to not have to work any harder. However, with speeding up, there
is only so fast that the parts can function at, and this provides the ceiling
for speeding it up.
3. State TWO major advantages of hard disk recording systems over digital
tape recorders.
On a hard disk recorder, it is far easier to access different sections of a
track; it is simply a case of pointing and clicking while observing a
graphical representation of the track. With tapes, you have to rewind and
forward to where you wish to edit. With hard disk, it is easy to simply undo
any changes that you don't like. There is an undo function to do this.
4. Describe THREE major operational advantages of having two modular digital
multitrack recorders such as the ADAT or DTRS formats over a format which
records sixteen tracks on the same tape on a single machine.
With two tapes you can make a copy for backup. You can also edit by copying
the track from one tape to another and using an offset. With 2 tapes you can
try out alternate takes of, say a vocal preformance by checking out how they
fare with the basic track on the other tape.
5. Explain why the punch in process on a hard disk recorder is more flexible
than that on an analogue or digital tape recorder.
The fundamental difference is between destructive and non-destructive. With
the hard disk you always have the facility of undoing the punch-in. This is
not possible on a tape recorder, there is no going back.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output b) why the `sync' output is required when
overdubbing.
Sync ensures that new tracks that are being recorded are in time with those
already on the tape. The sync output is required when overdubbing as the
record head and playback head are physically separate and a delay will be
heard if sync output is not selected.
7. It is common for a multitrack hard disk recording system to be able to
store more tracks in synchronisation than it can play simultaneously. Why is
this?
Yes it is. See question 1
8. Some hard disk recording systems have mixing facilities so that several
tracks can be mixed into a stereo output. If no other outputs are available
why must the system incorporate reverb internally?
If no other outputs are available, then there is no way that you could pass a
signal out to an external reverb unit and then pass it back to the system.
Using it internally would logistically be the only option.
9. What are the two major advantages of hard disk recording systems over
digital tape recorders?
See Q3
10. What piece of equipment is necessary to use a sequencer with a
multitrack tape recorder?
AN SMPTE time code generator will superimpose frames which denote hours
minutes and seconds onto the tape.
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position
Pointers when synchronising a sequencer to a tape recorder?
MTC is based on absolute time measured in seconds, minutes and hours as
opposed to tempo speeds as is the case with midi clocks. As such it more
reliably syncs the time code of the sequencer to the tape.
c) If MIDI Machine Control (MMC) is not used, describe briefly the two
distinct stages of operation when recording a piece of sequenced music to
multitrack tape.
The first stage is to "stripe" the tape, which is to format it with a time
code that the sequencer will recognise and be able to manipulate. The second
step will be to actually record the music onto the tape from the midi
devices. This can be done by adding the track of each instrument to the
tape, or by adding the whole mix onto 2 stereo tracks.
d) What is the advantage of MMC?
It enables the remote control of a hard disk recording system through a midi
cable.
e) In a system using MMC, while playback or recording progresses the
multitrack and sequencer will be running in sync. At this moment which is
master and which is slave?
I would say that the multitrack is the master at this point as the track
being reproduced in playback is coming from the multitrack.
11. You have been given an unlabelled tape to play which starts with a
warbling tone. What noise reduction system might have been used?
DBX?
b) You have been given an unlabelled tape to play which starts with noise.
What noise reduction system might have been used?
none?
c) Name three domestic noise reduction systems invented by the Dolby company.
Dolby B - the original noise reduction system used in home tape recorders.
10db of high-register noise reduction that had particular success with
eliminating tape his..
Dolby C - enabled double the tape hiss noise reduction (20db) and was offered
in mid-to-high range tape decks and video cassettes along with Dolby B.
Dolby S - This was a further evolution in noise reduction, enabling a 24db
reduction in tape hiss and adding in 10db reduction of low-frequency noise.
It also enabled the more accurate recording of signals at high-frequency
extremes.
d) Give the name of another fairly common analogue noise reduction system.
DBX. This works by taking the signal before it is committed to tape and
compresses the sound, squeezing out undesirable frequencies. It then expands
the cleaner sound when comitting it to tape
e) Where would you find the ATRAC digital noise reduction system?
On a mini disc recorder
12. When recording onto analogue or digital multitrack tape, in a situation
where synchronisation is going to be used, what procedure must be carried out
before any recording can begin?
You have to stripe the tape with SMPTE code, so that it is ready with a
real-time based time code to be synchronized with.
b) Your studio manager has given you a multitrack tape containing music and
timecode to copy. What must you do to ensure that the timecode is copied
correctly?
The recording level of the timecode must be perfect - this is between -5 and
-7 db. Otherwise the signal may turn out to be too high or too low. If it
is too high, it can bleed into other tracks, and if it is too low it may not
be picked up by the system it is being copied to.
c) A multitrack tape of a band with no sequenced instruments was striped with
timecode at the start of the session and has subsequently been edited? Would
it be good practice to use the existing timecode as a synchronisation
reference for the console automation system during the mix?
It would not be good practice, as the original time code may have been
altered and it will not be a reliable sync reference. It would be more
advisable to reinstall a time code for the automation mix down.
d) Referring to c) above, why would it not be a problem to re-stripe the tape
with timecode and erase the original timecode, even if the generator does not
have a jam sync function?
Jam-Sync regenerates the orginal time code. As the tape has been edited,
this will not be of any use to the new format of the track. A new time track
must be copied.
e) You have striped timecode on track 24 of an analogue tape and recorded a
bass guitar on track 23. When you try and synchronise a MIDI sequencer using
a cheap timecode to MTC convertor, the sequencer often stops or loses sync.
Why?
The bass guitar signal must be bleeding into the timecode track. This could
be due to the high levels that charcterise bass guitar signals. It might do
to keep the bass track further away.
13. When working with MIDI and multitrack tape, does the multitrack recorder
synchronise to the sequencer or does the sequencer synchronise to the
multitrack tape?
The sequencer synchronizes to the multitrack. This is dictated by the time
code allocated to the multitrack.
b) When working with an ADAT recorder, why wouldn?t you necessarily have to
stripe the tape with timecode to synchronise a sequencer?
ADAT already has time code attributed to it, so it will not be necessary to
stripe the tape.
c) Imagine that several tracks of a MIDI sequence have been transferred to
multitrack tape. The producer decides that he wants to varispeed the tape a
little faster. Should this be done before or after the remaining sequencer
tracks have been transferred to tape? Explain your answer.
I would say that all the sequencer tracks should be transferred to tape
before using varispeed to make certain tracks faster. If not, then the
chosen tracks to use varispeed on will have their pitch altered, and a lot of
work using pitch bend will be necessary to get the remaining tracks to match.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a
recording to vary. Explain why this is so.
Noise reduction entails encoding and decoding back the recorded sound. If
this is carried out on a number of different systems, the noise levels will
vary with each different system.
15. You have been asked to remix a song (in the sense of creating a
completely new version) originally made on multitrack tape in the early
1970s.
a) What would be the main problem in synchronising a sequencer to the
original tape?
Matching the exact time code with the tempo of the original might be inexact.
b) If you decided only to use the vocal track from the original recording,
how would you make the lines fit in time with your new MIDI sequencer
arrangement?
By recording them into a sampler and edit it based on the graphical
representations in the sufio editor. You could also use varispeed to stretch
the vocal to the point where its fit is perfect.
c) Suppose you want the song to be around 15% faster in tempo. What should
you do to speed up the vocals?
Use varispeed or timestretcher to speed up the vocal without altering the
pitch.
d) The record company decides that it wants to keep a lot of the original
instrumentation, but also likes your strict tempo MIDI sequence. What type
of equipment should you use to put everything together?
Use a multitrack to lay down all the individual instrumental tracks. Then
save the track into a midi sequencer and attribute the MIDI tempo to the
track.
16. You are working with a multitrack recorder that will slave to SMPTE/EBU
timecode from (for instance) a video machine, but has no other means by which
it may be externally controlled. Imagine you stop the master machine, rewind
the tape to the beginning and start playing. What will the multitrack do?
I would suppose that the recorder, as it is the slave to the video machine
would stop and then start up again when the tape starts up again. I would
expect it however not to have rewound, but to have added the track
contiguously from the end of the last one. |
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Thu Nov 06, 2003 12:06 am |
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mommi
Joined: 21 Apr 2003
Posts: 47
Location: Tallinn, Estonia |
Regarding to the question 16 about multitrack behaviour when SMPTE/EBU synced to the video tape machine, I noticed there is something I hadn't thought of before. Since SMPTE timecode is an absolute one, we might assume the multitrack would be able to understand from where the video machine had continued playing. Now the question remains, what would it do with that information. It seems, the multitrack could try to rewind itself after the video machine had started over, since it was only then that the multitrack got to know what was going on.
Ideas anyone? |
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Thu Nov 06, 2003 4:08 pm |
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ruiabreu
Joined: 15 Sep 2003
Posts: 12
Location: Portugal |
| recording techniques week10 |
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Hi Chris
Here are the answers.
l1. Explain why it is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously.
Usually on a multitrack hard disk recording system there is a possibility of recording various takes of the same instrument. All takes are synchronized but just one is set to play. You can jump from take to take until you find the best and set this take to play. This feature is usually called “virtual tracks”.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
In multitrack hard disk recording the audio tracks that are played are retrieved from the hard disk in a continuous manner. If you increase the speed of playing more data has to be retrieved from the disk on the same amount of time, and more load is applied to the processing power of the computer. As you increase the speed, the computer will eventually stop being able to handle that much information and hence play less tracks.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
In digital tape the tracks of a music piece are linked and in sync and you can’t cut and paste a part of a music and place it on another part as you can on hard disk recording.
In a hard disk recording you can instantaneously wind or rewind a music piece while in digital tape recorders you have to wait for the tape to be winded or rewinded.
4. Describe THREE major operational advantages of having two modular digital multitrack recorders such as the ADAT or DTRS formats over a format which records sixteen tracks on the same tape on a single machine.
These types of machines are maintenance intensive and are prone to a few crashes. If one machine stops working it’s better to have two machines in sync because you can continue your work although with only 8 tracks. If you have just one machine, you can’t continue your work until the machine is fixed.
You can use two machines separately in two audio projects at the same time and on different places. With one machine you can only work on one project at the time.
You can use the two machine setup to edit a part of the song and place it on another point of the music different from the first point. This is achieved by copying that music part from one machine to another and then by recording that part of the music from the second machine back to the first but on the song position you want.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder.
Because Punch in, in a hard disk recorder, is a non destructive process. If you are not happy with the recording of a punch in, you can undo it and the recording you had before was not erased. In digital or tape recorder once you record one part of a music it will erase the earlier part.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output
In analogue multi-track recorder, the record and play heads are a few inches apart from each other. The play head comes first and reads the tape and the record head comes next and records the input signal. ‘Sync’ output refers to the possibility of using the record head for both recording and playing. This way the material that is being played and the material that is being recorded are synchronized in time.
b) Why the `sync' output is required when overdubbing.
Overdubbing is the act of recording a track while hearing other tracks previously recorded. When recording overdubs you want the tracks you are recording synchronized with the previously recorded tracks. In analogue multi-track recorder this can just be done in ‘sync’ mode when the record head is used for both play and record.
7. It is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously. Why is this?
See answer of question 1.
8. Some hard disk recording systems have mixing facilities so that several tracks can be mixed into a stereo output. If no other outputs are available why must the system incorporate reverb internally?
Essentially what we are talking about here is a mixer less system. To incorporate external reverb via a reverb hardware unit you would need to connect it to auxiliary inputs and outputs of the stereo output channel. For this you would need a mixing console that you have not. Internal DSP reverb, if you have it, or host native software reverb, is what you need.
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
The ability of hard disk recording to instantly wind or rewind to any point of a song. In digital tape you have to wait for the wind/rewind process to take place and this takes time. Also the ability of hard disk recording to perform non-destructive recording. When you record a second take of an instrument recording and you are not happy with it you can undo the process and go back to the take previously recorded. Or you can edit the two takes and choose the best part of each take.
10.
a) What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
You need a synchronizer.
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?
When synchronizing a sequencer to a tape recorder, you usually make the tape recorder the master and the sequencer the slave. For a tape recorder you can use SMPTE (LTC) as the synchronization protocol. Because MTC is obtained from LTC timecode, there is a straightforward relation between then. An address time code on LTC is the same as the MTC derived from the LTC. In MIDI clocks and Song Position Pointers the relation would not be “one on one” with the master LTC timecode and the LTC-to-MIDI clock conversion would be more complex and so less reliable. Also the resolution of the MTC signal is higher than MIDI clock.
c) If MIDI Machine Control (MMC) is not used, describe briefly the two distinct stages of operation when recording a piece of sequenced music to multitrack tape.
Let’s consider you already have tracks recorded on the sequencer. You need to synchronize the two devices. First you strip a track (usually the track with highest number) of the multitrack tape machine with LTC time code using a special code generator machine. Second you synchronize both machines using a LTC-to-MTC converter device. You connect the output of the track with the LTC on the multi-track tape to the input of the converter device. Then connect the converter output to the input of the sequencer sound card or external box that handles synchronization signals. This signal is MTC and the sequencer can understand it and sync to it. Now you just have to press record on the tape machine as he is the master on this system.
d) What is the advantage of MMC?
You can do it all on the sequencer. The tape multi track recorder will behave like a slave and the transport tasks will be performed inside the sequencer.
e) In a system using MMC, while playback or recording progress the multitrack and sequencer will be running in sync. At this moment which is master and which is slave?
During playback and recording, the multitrack will be the master and the sequencer the slave. In the moment you press play and record, it is the sequencer the master. But in this moment the sequencer will send the information that you want to play of record to the multitrack and from this moment on it is the multitrack that becomes the master.
11.
a) You have been given an unlabelled tape to play which starts with a warbling tone. What noise reduction system might have been used?
Don’t know what a warbling tone is (my dictionary isn’t the most complete) but once, when I was using a noise reduction plug-in to clean an old song recorded on a 4 track cassette recorder, there were some artefacts that appeared on the song. Are those warbling tones?
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?
Maybe the Dolby B consumer nose reduction technique. This system was designed to reduce tape hiss but not so much low frequency noise such as hum and rumble.
c) Name three domestic noise reduction systems invented by the Dolby Company.
Dolby B. As stated before it is specialized on reducing tape hiss and reduces noise around 10dB at around 5 kHz but only 3 at 600 Hz.
Dolby C. It’s a consumer version of the professional Dolby SR and offers up to 20 dB of overall (all frequencies) noise reduction.
Dolby A was the original professional noise reduction method by Dolby. It reduces tape noise approximately 10 to 15 dB by dividing the audio spectrum into four separate bands. Each band has its own dynamic range processor. This way the presence of a high level signal on one band won’t interfere with detection circuits in another band.
d) Give the name of another fairly common analogue noise reduction system.
DBX noise reduction system.
e) Where would you find the ATRAC digital noise reduction system?
In a Mini-Disk system.
12. When recording onto analogue or digital multitrack tape, in a situation where synchronisation is going to be used, what procedure must be carried out before any recording can begin?
You must strip (record) a LTC (longitudinal time code) signal on one of the tracks (the highest number) on the multi track tape recorder.
b) Your studio manager has given you a multitrack tape containing music and timecode to copy. What must you do to ensure that the timecode is copied correctly?
When you copy a timecode the signal will be degraded and devices that rely on that signal to synchronize may not do it accurately. To resolve this issue you may route the time code track to a signal synchronizer generator with ‘jam sync’ mode enabled. In this mode the generator will receive a time code signal from the tape and output a brand new code signal equal to the one it is receiving but with no degradation.
c) A multitrack tape of a band with no sequenced instruments was striped with timecode at the start of the session and has subsequently been edited. Would it be good practice to use the existing timecode as a synchronisation reference for the console automation system during the mix?
I don’t think so. Time code as an address component that indicates where in the tape you are. If you edit a part of the song the address component will be misplaced and the multitrack would probably be confused. If you have no sequenced instruments you may want to add latter, then I don’t see a problem in just striping the tape again in the same track. Automation would have to be done all over again.
d) Referring to c) above, why would it not be a problem to re-stripe the tape with timecode and erase the original timecode, even if the generator does not have a jam sync function?
The tracks on tape are synchronized to each other. Synchronizing is important if you are using to different devices. In this case redoing striping will not change the time alignment of the tracks already recorded. In this case jam sync function isn’t really an issue because you are not recording a time code from one tape to another. You are simply erasing original time code with one that comes from the generator and as no degradation problems. It is brand new.
e) You have striped timecode on track 24 of an analogue tape and recorded a bass guitar on track 23. When you try and synchronise a MIDI sequencer using a cheap timecode to MTC converter, the sequencer often stops or loses sync. Why?
Probably the bass guitar on track 23 is spilling to the time code signal on track 24. The time code signal is an audio signal and the information on it as to be understood by the other synchronized machines. If external signal is added (like spilling) then the time code signal is disguised and may not be understood by the other machines.
13. When working with MIDI and multitrack tape, does the multitrack recorder synchronise to the sequencer or does the sequencer synchronise to the multitrack tape?
The sequencer synchronizes to the multi track recorder.
b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with timecode to synchronise a sequencer?
An ADAT recorder usually has a proprietary process of recording a time code signal in the process of formatting the tape for recording. You don’t need to strip a track since the time code signal will already be on the tape. The signal will be placed on a control track but I couldn’t understand if his means 8 tracks + 1control track or 7 tracks + 1 control track.
c) Imagine that several tracks of a MIDI sequence have been transferred to multitrack tape. The producer decides that he wants to varispeed the tape a little faster. Should this be done before or after the remaining sequencer tracks have been transferred to tape? Explain your answer.
You can do it before or after the remaining sequencer tracks are transferred. The sequencer is the slave and syncs to the MTC signal that comes from the multitrack via the LTC-to-MTC converter. If you increase the tape speed the sequencer will increase the speed also. This is for a MIDI sequencer only. With Audio/MIDI sequencer this would be another story, but in this case why would you need a multitrack anyway?
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
They use a processing method called compansion (mix of the words compression and expansion). In this process the signal is compressed (the dynamic range is reduced) before it is recorded. This allows the signal being recorded to tape at levels higher than the tape noise. When the signal recorded is played back it passes an expander that restores the signal to his original dynamic level. In this process the tape noise his also expanded to lower levels.
15. You have been asked to remix a song (in the sense of creating a completely new version) originally made on multitrack tape in the early 1970s.
a) What would be the main problem in synchronising a sequencer to the original tape?
For synchronizing a sequencer to the multitrack recorder used to record the original tape you need a track to strip the LTC time code. You may not have a track that is free and you may have to erase one of the original tracks.
b) If you decided only to use the vocal track from the original recording, how would you make the lines fit in time with your new MIDI sequencer arrangement?
My first choice would be to record the original vocal tracks to the audio sequencer (assuming you are using an audio and not a MIDI only sequencer), and then simply change the tempo of the MIDI arrangement until it fits the vocal tracks. Or you could manually edit the MIDI arrangement until it perfectly fits each part of the vocal tracks. Or, if you want to maintain the MIDI tempo you splice the vocal track and move the parts of the vocal track to the precise points in time you want.
With a multitrack/sequencer synchronized system there is the possibility of simply changing the tempo of the MIDI arrangement in the sequencer until it matches the vocal tracks. The MTC signal the sequencer receives from the multitrack in as absolute signal and says nothing about beats and bars. I’m not shore about this possibility.
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
I would speed up the tape of the multitrack recorder. The sequencer would have to catch up since the sequencer is the slave. The problem here is the increase of pitch of music. But the question says nothing about this being a problem. Still you can apply a pitch shifter to the vocal track to account for this increase of pitch.
d) The record company decides that it wants to keep a lot of the original instrumentation, but also likes your strict tempo MIDI sequence. What type of equipment should you use to put everything together?
Again my first option would be to record the original tracks as audio tracks on the audio sequencer and then simply adjust the tempo of the MIDI parts until it fits the tempo of the original tracks. Changing tempo in the original tracks is more difficult in that the tracks have an inherent tempo and if you change the tempo the pitch of the song would be changed.
The other option would be to strip a LTC time code sacrificing a track from the multitrack recorder, then connect the output of the time code track to the input of a synchronizer. The synchronizer output will route to the input of the sequencer that can handle synchronization.
16. You are working with a multitrack recorder that will slave to SMPTE/EBU timecode from (for instance) a video machine, but has no other means by which it may be externally controlled. Imagine you stop the master machine, rewind the tape to the beginning and start playing. What will the multitrack do?
The slave multitrack will catch up the master device but just from the moment you hit play and not during rewind. This happens because when performing rewind the tape isn’t reading the time code audio track and the synchronization signal isn’t sent to the slave. This happens only when play is pressed. The multitrack will rewind as fast as it can until it catches up the master and then goes to play mode and compare his time code to the time code of the master. If both devices are in the same point in time then they are in sync. If the multitrack didn’t exactly hit the moving target them it will wind or rewind until it reaches the exact point of play of the master. This process is repeated until both machines are in sync. This process is controlled by the synchronizer. |
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Sat Nov 08, 2003 9:26 am |
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Fenderocks
Joined: 09 Aug 2003
Posts: 26
Location: Music City, USA |
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Week 10 - Synchronisation
1. Explain why it is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously. The reason this is allowed is because you can record more tracks for the option to choose the best ones for playback or mixing.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster. The reason some hard disk multitrack recording systems can only play a little faster is because the faster the playback is it will involve greater data retrieval rates. And by how fast the data can be read and transferred plays a great role on how many tracks can be played at one time.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
First- would be it is much easier to edit hard disk recording systems vs. digital tapes, because you can just go to the menu and select what you want it to do, as for as coping and pasting adding effects, and being able to select the undo for anything you don’t like.
Second- would be that you can go to any point of the recording by a click of a button vs. rewinding tapes to get to the stop where you want to be.
4. Describe THREE major operational advantages of having two modular digital multitrack recorders such as the ADAT or DTRS formats over a format which records sixteen tracks on the same tape on a single machine. First you can backup very easily the data you want by having two tapes. Second you can edit the project a lot easier by coping it on 2 tapes vs. one. Third you can have alternate tracks for which one sounds better and which doesn’t.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder. Simply because on a digital tape recorder you can’t undo the punch if it didn’t sound the way you wanted... That’s the reason the punch-ins are better used on a hard disk recorder because you have the option of the undo button and no worries about destructive and non destructive audio.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output – This term means that when recording a new track off the basic tracks it makes sure that it is in time with those already on the tape
b) why the `sync' output is required when overdubbing. A delay would accrue because the record head and the playback head are separate if the sync output is not being used.
7. It is common for a multitrack hard disk recording system to be able to store more tracks in synchronization than it can play simultaneously. Why is this? The reason this is allowed is because you can record more tracks for the option to choose the best ones for playback or mixing.
8. Some hard disk recording systems have mixing facilities so that several tracks can be mixed into a stereo output. If no other outputs are available why must the system incorporate reverb internally? Well at this point you have no other option because if there is no output for an external reverb unit there is no way you can pass the signal. So you have to the reverb internally because there is no other way.
9. What are the two major advantages of hard disk recording systems over digital tape recorders? First- would be it is much easier to edit hard disk recording systems vs. digital tapes, because you can just go to the menu and select what you want it to do, as for as coping and pasting adding effects, and being able to select the undo for anything you don’t like.
Second- would be that you can go to any point of the recording by a click of a button vs. rewinding tapes to get to the stop where you want to be.
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder? SMPTE or MTC is what comes to mind. The time code generator will record the frames which denote hours, min, and sec on the tape. If the sequencer can not read the SMPTE it will read the MTC (MIDI time code).
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronizing a sequencer to a tape recorder? Well the MTC is based on absolute time measured in seconds, hours and min. With the MIDI clocks and SSP based off tempo speeds. This way it is a more reliable sync with time code of a sequencer.
c) If MIDI Machine Control (MMC) is not used, describe briefly the two distinct stages of operation when recording a piece of sequenced music to multitrack tape. Stripe the tape would come first and is the way to format the tape to a time code that the sequencers will response to. Then record the music or song to the tape with MIDI devices would be the second step.
d) What is the advantage of MMC? The MMC is a way to enable the remote control of a hard disk recording system through a simply MIDI cable. Even two or more MIDI devices can function by just the MMC, but not used for synchronizing the signal, it must be synced through another device.
e) In a system using MMC, while playback or recording progresses the multitrack and sequencer will be running in sync. At this moment which is master and which is slave? The Multitrack recorder would be the master and the slave would be the sequencer.
11. You have been given an unlabelled tape to play which starts with a warbling tone. What noise reduction system might have been used? I don’t think know one knows what this is unless you ran across it before or unless you where the person who recorded it.
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used? None most likely, the function of noise reduction is to reduce the noise, not starting off with noise. But I’m not sure.
c) Name three domestic noise reduction systems invented by the Dolby company.
First-Dolby b with a 400hz starting from and a 10hz reduction tape hiss
Second- Dolby c is more expressive then the first one but goes down to 100hz and has anti-saturation circuitry to prevent hf overload in the signals with high hf content, with being able to have 20hz noise reduction.
Third- Dolby s, like the Dolby c but with filter technology, Mucho Denero $$$
d) Give the name of another fairly common analogue noise reduction system. DBX is a great one to use with the functions of high-frequency pre-emphasis and allow compression over the whole dynamic range.
e) Where would you find the ATRAC digital noise reduction system? Adaptive transform acoustic coding and is found on mini-discs. Developed by Sony and by taking in account of the human ear this compressed audio has virtually no loss in sound quality.
12. When recording onto analogue or digital multitrack tape, in a situation where synchronisation is going to be used, what procedure must be carried out before any recording can begin? The tape must be striped with an SMPTE time code, Allowing the tape to run in sync.
b) Your studio manager has given you a multitrack tape containing music and timecode to copy. What must you do to ensure that the timecode is copied correctly? A time code generator, with jam syncing. That Jam syncing is a way of taking in a timecode and regenerating it to allow a copy of the original.
c) A multitrack tape of a band with no sequenced instruments was striped with timecode at the start of the session and has subsequently been edited? Would it be good practice to use the existing timecode as a synchronisation reference for the console automation system during the mix? Not a good idea because in could have had a different time code entered witch may cause it to be out of sync.
d) Referring to c) above, why would it not be a problem to re-stripe the tape with timecode and erase the original timecode, even if the generator does not have a jam sync function? It must have a new time track entered because the tape has been edited.
e) You have striped timecode on track 24 of an analogue tape and recorded a bass guitar on track 23. When you try and synchronise a MIDI sequencer using a cheap timecode to MTC convertor, the sequencer often stops or loses sync. Why? The bass signal is bleeding into the timecode track. Best used for the bass being further away.
13. When working with MIDI and multitrack tape, does the multitrack recorder synchronise to the sequencer or does the sequencer synchronise to the multitrack tape? The sequencer is synchronized to the multitrack recorder. This is what the time code allows.
b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with timecode to synchronise a sequencer? ADAT already has a time code to it and would not need for the tape to be striped.
c) Imagine that several tracks of a MIDI sequence have been transferred to multitrack tape. The producer decides that he wants to varispeed the tape a little faster. Should this be done before or after the remaining sequencer tracks have been transferred to tape? Explain your answer. This should be done after all the sequencer tracks have been transferred and the reason why is because since some tracks have already been recorded by changing it now would cause some of the tracks to have different tuning.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so. The reason dbx and Dolby cause the noise level in a recording to vary because dbx and Dolby adapt to signal characteristics. They only respond or work better with the signals that don’t have high enough level near the frequency region of noise. There is less need for these systems when the signal is already high.
15. You have been asked to remix a song (in the sense of creating a completely new version) originally made on multitrack tape in the early 1970s.
a) What would be the main problem in synchronising a sequencer to the original tape? Well you’ll probaley have problems with the tempo and by using the synchronising of sequencer getting to two together could cause a problem as well.
b) If you decided only to use the vocal track from the original recording, how would you make the lines fit in time with your new MIDI sequencer arrangement? First record them into a sampler and edit based to fit the appropriate time or you could stretch using varispeed to the point where it fits perfectly.
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals? Varispeed or time stretch to the intended tempo to fit.
d) The record company decides that it wants to keep a lot of the original instrumentation, but also likes your strict tempo MIDI sequence. What type of equipment should you use to put everything together? A
a muititrack recorder and throw all the separate instruments in separate tracks, then save the tracks to a MIDI sequencer and then use the MIDI tempo and apply it to the tracks.
16. You are working with a multitrack recorder that will slave to SMPTE/EBU timecode from (for instance) a video machine, but has no other means by which it may be externally controlled. Imagine you stop the master machine, rewind the tape to the beginning and start playing. What will the multitrack do? The tape would stop together with the master and the slave. Then the master would start over again thus making the slave start over with it there as the muititrack will then receive timecodes and contained where it stopped. |
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Sun Nov 09, 2003 8:36 am |
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julesf
Joined: 31 Aug 2003
Posts: 58
Location: Southampton, UK |
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Better late than never 
RT Week 10
<b>1. Explain why it is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously.</b>
These virtual tracks allow for multiple takes to be made in a non-destructive manner. The takes can be analysed and the best one used for the recording. It is also normally possible for a take to be made up from various virtual tracks. All editing is non-destructive and does not alter of effect the original recorded track or further virtual tracks. This enables safe experimentation to be carried out.
<b>2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster. </b>
This is due to the file handling capability of the system. Tracks must playback in real time. The faster the playback of the song, the faster the digital audio needs to stream from the hard disk. Also large numbers of tracks will slow down the performance of the recorder. Slowing down the playback actually reduces the loading on the hard disk system as there is less demanding on the system to buffer digital audio data to the DAC.
<b>3. State TWO major advantages of hard disk recording systems over digital tape recorders. </b>
Most Digital hard disk recorders are "pointer based" and possess more complex editing tools which tape based systems such as "DASH" do not have. Most also have virtual tracks which allow multiple non-destructive takes on each track, normally eight. More data can be stored on modern large hard disks, Hard disk recorders also have improved reliability over tape based systems. Hard disk recorders are faster at locating than tape machines as they do not need to forward wind or rewind the tape each take.
<b>4. Describe THREE major operational advantages of having two modular digital multitrack recorders such as the ADAT or DTRS formats over a format which records sixteen tracks on the same tape on a single machine. </b>
Two machines provide a method of making back ups of tapes.
Alternative takes can be tried in a non destructive method by replacing the tape with a fresh one while playing back the basic tracks from the original tape in the primary machine.
More complex editing can be performed by flying tracks back and forth between machines.
<b>5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder. </b>
The process is much faster as you do not need to wait for the tape to rewind for each punch in
If the hard disk recorder has a graphical display then it is also much easier to locate and set the punch in point.
<b>6. With reference to an analogue multi track recorder briefly explain
a) the term `sync' output
b) why the `sync' output is required when overdubbing. </b>
The sync output uses the record head as a temporary sync head to allow monitoring of the recorded audio tracks
In sync with the audio to be recorded. This is required due to the distance between the record head and the playback head on the head block. If the replay head was used for monitoring while overdubbing then the resulting audio would playback out of sync. The quality of the audio from the sync head is not as good as that from the playback head, however this is not a problem as the audio is just for monitoring purposes. All of the audio tracks can be replayed from the playback head in high quality during mix down.
<b>7. It is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously. Why is this?</b>
Yes, most machines offer Virtual tracks. The machine can only playback it's total number of tracks at once but the virtual tracks allow for multiple takes to be made on the same track. You can record say 8 vocal takes on track 1. Then you may audition the takes and use the best one for mix down. Some systems allow you to edit sections of any of the virtual tracks and main track to compile a best take. This normally requires cut and paste to edit phrases from various takes on the virtual tracks.
<b>8. Some hard disk recording systems have mixing facilities so that several tracks can be mixed into a stereo output. If no other outputs are available why must the system incorporate reverb internally? </b>
If the recorder has no other outputs it would not be possible to route say just the vocal to an outboard effect. You would only be able to treat the entire mix with reverb, which may be unsuitable for your project. If the unit has an internal effects processor it will be capable of routing and wetting just the selected tracks such as vocal.
<b>9. What are the two major advantages of hard disk recording systems over digital tape recorders? </b>
See 3.
<b>10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder? </b>
A synchroniser unit that can "stripe the" analogue tape with time code which the sequencer can then follow.
<b>b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?</b>
MTC is the MIDI version of SMPTE, it is much more functional than MIDI Clock with SPP. When the master is fast-forwarded or re-wound the slave will immediately lock on to the direct reference point. If used with MMC the sequencer will chase the recorder during forward wind and rewind and then lock on to the reference point accurately when play is pressed.
<b>c) If MIDI Machine Control (MMC) is not used, describe briefly the two distinct stages of operation when recording a piece of sequenced music to multitrack tape.</b>
The tape must be striped with the audio pulsed data and then the time coded audio track can be played back to the time code unit, which will in turn send clock pulses to the sequencer, which must be set to slave to MIDI clock. The sequenced music may now be recorded to the audio multitracker as individual tracks or as a mix from the desk.
<b>d) What is the advantage of MMC? </b>
MIDI MACHINE CONTROL when used in conjunction with MIDI TIME CODE will carry out full synchronisation functionality to a very high resolution. The MMC sends messages regard the transport controls such as PLAY, STOP, FORWARD, REWIND, etc which the slave will respond to. The MTC locks on to the exact position and stays in sync when record or play is pressed.
<b>e) In a system using MMC, while playback or recording progresses the multitrack and sequencer will be running in sync. At this moment which is master and which is slave? </b>
Normally the Multitrack machine is the master as most don't respond to time code?
<b>11. You have been given an unlabelled tape to play which starts with a warbling tone. What noise reduction system might have been used? </b>
Dolby S ?
<b>b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?</b>
DBX The signal has not been expanded so the tape noise comes through.
<b>c) Name three domestic noise reduction systems invented by the Dolby company. </b>
Dolby B typically 10 dB reduction Dolby C Typically 20dB reduction Dolby S More advanced than the others.
<b>d) Give the name of another fairly common analogue noise reduction system.</b>
DBX This uses a compander (Compressor Expander) system to control tape noise.
<b>e) Where would you find the ATRAC digital noise reduction system? </b>
This system is used exclusively on Mini Disc Recorders. The system is an algorithm that reduces the amount of audio data produced while recording without significantly reducing the audio playback quality, a kind of intelligent compression.
<b>12. When recording onto analogue or digital multi track tape, in a situation where synchronisation is going to be used what procedure must be carried out before any recording can begin? </b>
One track must be encoded (Striped) with the time code signal which will be converted to
<b>b) Your studio manager has given you a multi track tape containing music and time code to copy. What must you do to ensure that the time code is copied correctly?</b>
Jam sync the time code. The system will read the time code on the source tape and regenerate the correct striping to the copy tape.
<b>c) A multitrack tape of a band with no sequenced instruments was striped with time code at the start of the session and has subsequently been edited? Would it be good practice to use the existing time code as a synchronisation reference for the console automation system during the mix? </b>
It would surly be more sensible to re-stripe the time code prior to starting automated mixes.
<b>d) Referring to c) above, why would it not be a problem to re-stripe the tape with time code and erase the original time code, even if the generator does not have a jam sync function</b>
Because the existing time code is not being used for any relevant referencing at this point. It can be erased and re-striped without fear of loss of sync.
<b>e) You have striped time code on track 24 of an analogue tape and recorded a bass guitar on track 23. When you try and synchronise a MIDI sequencer using a cheap time code to MTC converter, the sequencer often stops or loses sync. Why? </b>
Could it be that due to the low frequency high amplitude recording on track 23 there is spill being induced into track 24 which is upsetting the MTC converter. Being a cheap unit it does not have the ability to "Fly Wheel" Through the points where the code is temporally lost.
<b>13. When working with MIDI and multitrack tape, does the multitrack recorder synchronise to the sequencer or does the sequencer synchronise to the multitrack tape?</b>
The sequencer syncs to the multitrack tape as this usually has to be the master and the Sequencer is the slave.
<b>b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with time code to synchronise a sequencer? </b>
ADAT Recorders support a native time code generator as part of the recorder. This is usually used to sync multiple ADAT machines together but can be used to extract MTC and MMC information if used with the Alesis BRC or a third party synchroniser such as JL Coopers DATA sync 2.
<b>c) Imagine that several tracks of a MIDI sequence have been transferred to multitrack tape. The producer decides that he wants to varispeed the tape a little faster. Should this be done before or after the remaining sequencer tracks have been transferred to tape? Explain your answer. </b>
This should be done after the remaining tracks have been recorded to tape. When the varispeed is increased the recorded tracks will raise in pitch. The MIDI tracks on the sequencer will just speed up but will stay the same pitch.
Also the recorded tracks and the remaining MIDI tracks will probably go out of sync.
<b>14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so. </b>
DBX and the various dolby systems work in various ways to attempt to reduce tape noise levels. The actual performance is very much dependent upon the noise reduction system, the tape machine, the tape quality, the condition of the tape machine heads, and the type of music being reproduced. Therefore it is not unusual to here varying degrees of background noise with the systems.
<b>15. You have been asked to remix a song (in the sense of creating a completely new version) originally made on multitrack tape in the early 1970s.
a) What would be the main problem in synchronising a sequencer to the original tape? </b>
The original recording may have been made without the use of any time code or click tracks, so it will not be tempo accurate and it is not likely that it will be possible to sync to static time code striping.
<b>b) If you decided only to use the vocal track from the original recording, how would you make the lines fit in time with your new MIDI sequencer arrangement? </b>
It would be best to chop the vocal parts up into individual phrases and place the relevant phrases against the backing track. Each short phrase will not have time to go out of sync (al la Elvis Vs JXL)
<b>c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?</b>
The vocals may be time stretched to meet the new tempo. Time stretching is good if only a small increase is required, however if the increase is too large then the sound quality will deteriorate.
<b>d) The record company decides that it wants to keep a lot of the original instrumentation, but also likes your strict tempo MIDI sequence. What type of equipment should you use to put everything together? </b>
A DAW is the best tool for this job. May be Pro Tools, Logic audio or Cubase. Play the parts into the DAW and then use the editing facilities to compile the final track. Time stretching and numerous other tools will be available and native to quality DAW's.
<b>16. You are working with a multitrack recorder that will slave to SMPTE/EBU time code from (for instance) a video machine, but has no other means by which it may be externally controlled. Imagine you stop the master machine, rewind the tape to the beginning and start playing. What will the multi track do?</b>
I am confused about this one like my fellow bunnies. My feeling is that the Slave will try and catch up by rewinding itself, however it will only attempt to do this once the master has started to play form the new point. During the
Rewind of the master machine the slave would lose time code, it may spend time trying to find the time code
By speeding up and slowing down. It may stop with an error. I guess that individual machines would handle the situation of lost time code differently according to manufactures program.
Cheers,
Jules |
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Fri Nov 14, 2003 5:48 am |
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