ben m
Joined: 15 Sep 2002
Posts: 337
Location: UK |
| Week 6 - Sampling 1 |
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Ok, and onto Sampling we go...
01- What are the logistical disadvantages of multisampling?
02- What is the importance of 'zero crossing' with sampled material?
03 - What problems may there be with sampled material from vinyl in terms of pitch/tempo?
04 - What are the benefits of multisampling?
05 - What are the advantages of USB connectivity for a sampler?
06 - Why do some samplers offer SCSI connectivity?
07 - What is 'tracking'?
08 - Why might an LFO be used with a sample?
09 - What filters are commonly offered with contemporary samplers?
10 - How do 'soft samplers' such as Gigasampler store their samples?
11 - Why are Zip Drives used with some hardware samplers?
12 - How can a sampler be used to add a 'vinyl effect' to a song?
13 - What benefits do samplers with multiple physical outputs have?
14 - What are the benefits of working with mono samples over stereo samples?
15 - What MIDI control messages can a typical sampler read?
16 - How can an instrument with a long sustain be created from an instrument with a short sustain using a sampler?
17 - Aside from a MIDI lead, what other connections are (or can be) made from a hardware sampler?
18 - How does a hardware sampler ensure that there is no latency?
19 - How can sample looping be used to save storage space?
20 - What are the main requirements of a glitch free loop?
21 - Why are closed and open hi-hats often sent to the same mute group?
22 - On hardware samplers, how much sampletime would you typically get out of 64MB storage?
23 - How might you achieve a chorus effect using a sampler that does not have an effects section?
24 - How might you soften the start of a drum sample (single hit)?
25 - In which phase(s) of the envelope (attack/decay/sustain/release) might you place the loop in a sample?
26 - Describe the differences in sound between a multi-sampled piano and a real piano.
27 - State the two main criteria for the successful looping of a single sampled note that is consistent in level and harmonic content.
Good Luck! |
Mon Oct 03, 2005 1:40 pm |
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Polarman
Joined: 24 Jun 2005
Posts: 55
Location: Barbados |
| Sampling 1 |
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01- What are the logistical disadvantages of multisampling?
The logistical disadvantages of multisampling are:
a) that more memory is used since more samples are used to recreate the instrument.
b) that more disk space is used. Since each instrument uses more samples, more disk space is needed to store instruments.
c) it takes longer time to record and set up since more samples from the instrument has to be recorded and they must have different keys addressed to them.
02- What is the importance of 'zero crossing' with sampled material?
The zero crossing discussion is not completely true. Zero crossing should only be used when the waveform shapes at the beginning and end of the loop DON´T match up in level, shape and phase. If they don´t match up you're quite likely to end up with a click at the sample loop point. Clicks can be MINIMISED by looping at 'zero-crossing' points (the point where the electrical signal crosses over from being positive to negative or vice versa) but even if that is done, some clicks will probably still be heared.
To get rid of the clicks some samplers have crossfade looping that instead of the end of the loop switching abruptly to the start, the sampler computes a gradual transition by fading out one end of the loop as the other fades in.
03 - What problems may there be with sampled material from vinyl in terms of pitch/tempo?
If the vinyl record its warped there will be tempo and pitch changes. The motor, if it is not correctly calibrated, can play in varying speeds.
04 - What are the benefits of multisampling?
The benefits with multisampling are that the original sampled source can be more correctly replayed. The more samples used to recreate a sound the more alike to the original source. This is because sounds become very unnatural when transposed far from their original pitch when you're trying to capture a real instrument such as a violin, gutair piano etc. , you only have to move a few semitones to either side of the note's original position and the sample starts to sound quite bad. If a sampled instrument sounds natural for only a couple of semitones either side of its original pitch, the only way to maintain a natural sound is to take several samples of the original instrument at different pitches and use each sample over a limited part of the keyboard. To get it to sound even more natural velocity switching or velocity crossfading can be used, where you take more than one sample for each pitch (note), Samples form the instrument playing loud to samples playing quite and then use key velocity to control which sample should be played back.
05 - What are the advantages of USB connectivity for a sampler?
With USB connectivity on a sampler you can connect external drives or connect an ASCII keyboard for easier file naming. A USB port can also be used to connect the sampler to a computer where you can edit the samples graphically with a software, transfer files to and from the sampler and organise libraries. Samples can be edited as standard wav files and sequences can be converted to standard midi files.
06 - Why do some samplers offer SCSI connectivity?
The SCSI connectivity on a sampler is usually used to connect an external SCSI drive or ZIP-drive. This makes it fast and easy to write and read samples. It’s also possible to connect a CD-ROM or connect the sampler to a computer with SCSI connectivity.
07 - What is 'tracking'?
When you play back a sample at a higher pitch, the whole harmonic structure of the sound is moved up. This means that the highest sound in one keygroup will sound brighter than the lowest note in the next keygroup up. If the keygroups are narrow this effect will not be noticed so much, but if you're using only one or two keygroups per octave you need to use the tracking filters set up with a negative value, so that as you move up a keygroup, the top end is tamed slightly. Some samplers allow you to crossfade from one keygroup to another, but this reduces polyphony and may produce unnatural chorus effects on solo instruments.
08 - Why might an LFO be used with a sample?
The LFO on a sampler lets you to change the pitch, tonal-quality and volume even in real time. To use the LFO to control filters is used a lot in modern music.
09 - What filters are commonly offered with contemporary samplers?
Filters: low-pass/band-pass/high-pass with dynamic resonance.
10 - How do 'soft samplers' such as Gigasampler store their samples?
Software samplers like Gigasampler, Kontakt and Halion store their samples on the harddrive. Each of them has it own format. Normally each sampler can import samples from other formats or play, wav, aiff files etc.
11 - Why are Zip Drives used with some hardware samplers?
Zip drive is a quick and easy way to save and load samples.
12 - How can a sampler be used to add a 'vinyl effect' to a song?
One way to get a vinyl effect in a song is to take a sample on a silent part (here silent means only the sound from the actual vinyl, no music...) of the record and loop that to get the noise from a vinyl record. This noise can then be mixed with the song.
13 - What benefits do samplers with multiple physical outputs have?
Multiple separate outputs on a samplers is good because then you are able to separate different sounds and be able to add effects or process each sound.
14 - What are the benefits of working with mono samples over stereo samples?
Mono samples take up half the RAM compared to stereo samples. Stereo samples are much harder to loop since the right and the left channel doesn’t have the exact envelope. Maybe you get a good match with looping the left channel but not the right channel.
15 - What MIDI control messages can a typical sampler read?
A typical sampler can read these kinds of midi signals:
Bank select, note on, note off, program change and velocity.
16 - How can an instrument with a long sustain be created from an instrument with a short sustain using a sampler?
One way to create a longer sustain on a sampled instrument is to loop the sustain part of the sample.
17 - Aside from a MIDI lead, what other connections are (or can be) made from a hardware sampler?
Other connections then MIDI can be SCSI, Fire wire and USB
18 - How does a hardware sampler ensure that there is no latency?
A hardware sampler works with samples stored in the RAM with fast access time. The samples used are preloaded in the memory.
19 - How can sample looping be used to save storage space?
To save storage space it’s possible to save the sample until the sustain phase and loop that phase instead of saving the whole sample. Since the loop is using the same data over and over no extra space is needed for that part.
20 - What are the main requirements of a glitch free loop?
The beginning and the end of the loop should have the same amplitude and phase, which means the same slope.
21 - Why are closed and open hi-hats often sent to the same mute group?
The closed and the open hi-hat should not be played at the same time in a natural setup of a drumset. So they are sent to the same mute group so that the open hi-hat sound mutes the closed hi-hat sound and vice versa.
22 - On hardware samplers, how much sampletime would you typically get out of 64MB storage?
If we are sampling with 44.1 KHz and 16 bit in mono then, one minute in bytes would be 44100x16x60 divided by 8 = 5292000. To convert this into Mb we have to divide twice with 1024 => 5.05 Mb.
In our case it will look like this if X= sample time in seconds:
44100x16x X divided by 8 = 64x1024x1024 => X= (64x1024x1024x8) / 44100x16 =>X = 761 seconds or divided by 60 => 12.67 minutes
If you are using stereo sampling you have to divide X with two => 6.33 minutes.
23 - How might you achieve a chorus effect using a sampler that does not have an effects section?
The simplest way to achieve a chorus effect on sampler is to doubble the sample and modulate the pitch of one of them with the LFO with a frquency around 3Hz. Normally you also need to delay the copied signal by 20-30 ms but since this is a sample the delay part of the chorus effect has been done just by changing the pitch.
24 - How might you soften the start of a drum sample (single hit)?
To soften a drum sample you can set a slightly longer attack time.
25 - In which phase(s) of the envelope (attack/decay/sustain/release) might you place the loop in a sample?
Normally the best place to place a loop in a sample is the sustain phase where you normally can find a place where the sound is as stable as possible.
26 - Describe the differences in sound between a multi-sampled piano and a real piano.
I am not sure what you mean by difference in sound…
There are many well known multi sampled pianos today such as EW Bosendorfer 290, Steinbergs The Grand 2, Best Service Galaxy Steinway etc. If we take for example Galaxy Steinway a multi sampled piano sampled in 48 KHz and 24 bit, it uses ten velocity layers and sample lengths up to 40 seconds.
The problem with multisampled pianos is that they can't really duplicate the tone and touch (since you are probably using a midi keyboard) of a real piano. Individual notes may be quite accurately reproduced, but the tone of notes sounding together, as in an acoustic piano, with complex harmonics mixing and resonating against a flexible wooden soundboard, cannot be matched. Most music sounds rather sterile played on a sampled piano."Touch Sensitivity" and "Weighted Action" is not the same thing as the sophisticated inner mechanism, or "action", of an acoustic piano. Sampled pianos simulate the touch of pianos. They don't provide the same feedback or responsiveness to the playing, so the performance range is limited.
27 - State the two main criteria for the successful looping of a single sampled note that is consistent in level and harmonic content.
The beginning and the end of the loop should have the same amplitude and phase (slope).
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Sources:
http://www.soundonsound.com/sos/1996_articles/jan96/samplebasics1.html
http://www.soundonsound.com/sos/1997_articles/sep97/samplebasics.html
http://www.soundonsound.com/sos/1996_articles/jan96/samplebasics1.html
http://www.concertpitchpiano.com/DigitalVsAcoustic.html
http://www.harmony-central.com/Effects/Articles/Chorus/
http://www.soundonsound.com/sos/may01/articles/catchphrase2.asp
http://www.soundonsound.com/sos/1996_articles/mar96/samplingbasics3.html
http://zonicweb.net/music/musictechnologydictionary2.htm#twenty
http://www.akaipro.com/productsMPC4000.html |
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Sat Oct 08, 2005 1:49 pm |
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AndyBarber
Joined: 09 Sep 2005
Posts: 18
Location: North Wales |
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Posted: Mon Oct 03, 2005 11:40 pm Post subject: Week 6 - Sampling 1
Andy Barber
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01- What are the logistical disadvantages of multisampling?
Sampling an instruments sound at various keys/pitches (multisampling). The samples can be assigned to their respective keys within a sampler giving a virtual copy of the instrument that can be played back at will using MIDI. Compared to a synthesis emulating an instrument, multisampling requires many large size files.
02- What is the importance of 'zero crossing' with sampled material?
When sampler isn’t in one-shot mode it is looped continuously until the key is released. In order for the looping to be smooth the start n end points of the sample need to match sonically. A zero crossing point is where points in the sample have momentarily zero energy. Placing the start and end of the loop at zero crossing points helps smooth out the loop. Cross fading also helps with smoothing and is needed for stereo samples.
03 - What problems may there be with sampled material from vinyl in terms of pitch/tempo?
Playing vinyl allows you to control the pitch/tempo of a record. When sampled it would be difficult to determine what key the sample would be in, or if its in key at all.
Samples cannot be taken at multiple pitches like you can do with a piano. The length and timbre of the sample is distorted when recorder’s tempo is changed
When sample is transposed up or down more than a few semi-tones it starts to sound unrealistic
Vinyl gives raw feel to samples and allows you to scratch them.
04 - What are the benefits of multisampling?
Provided producers with analogue, real instrument and other hardware sounds in a soft synth environment
Much cheaper than repeatably hiring musicians to play and record their instruments for your mix
05 - What are the advantages of USB connectivity for a sampler?
USB lets computer control external sampler and is much faster than MIDI. Interface makes it easy to get data to and from the sampler and computer DAW. Also allows you to use a sample editor to edit samples on screen, while maintaining excellent sound quality.
Samples must be loaded from permanent storage into samplers internal RAM.
06 - Why do some samplers offer SCSI connectivity?
An SCSI connection allows samples to be uploaded and downloaded to an from an external hard drive, CD rom, floppy drive or computer. SCSI also provides a method of joining samplers together
07 - What is 'tracking'
Music making software ‘tracker’ that produces some form of module music files.
It consists of a fixed, sample based synthesis algorithm and a strictly metric, multi-channel score.
The software allows the user to arrange sound samples stepwise on a timeline across several monophonic channels. Basically step sequencing of samples.
08 - Why might an LFO be used with a sample?
An LFO in a sampler is again used as a modulator. It can be used to modulate many variables in a sampler including the amplitude of a sample and the filter acting on it.
09 - What filters are commonly offered with contemporary samplers?
Usually low/band/high pass filters with selectable modes 12/18/24 dB/octave
Filtering can also be used to tidy up noisy samples, bringing out speech from background noise
10 - How do 'soft samplers' such as Gigasampler store their samples?
Giga sampling introduced the concept of disk based sampling. Software designed to stream samples directly from harddrive rather than squeezing them in to RAM. Allows much more sample time and is only restricted by CPU.
11 - Why are Zip Drives used with some hardware samplers?
Zip drives are required when a hardware sampler doesn’t have an internal hard drive or CD rom to supply and store samples.
12 - How can a sampler be used to add a 'vinyl effect' to a song?
Using noise samples like crackling can add a subtle vinyl effect to a sound
13 - What benefits do samplers with multiple physical outputs have?
Digital technology allowed samplers to have polyphonic separate outputs. Different groups of samples can be assigned to separate channels on a mixer. They can then be processed separately.
14 - What are the benefits of working with mono samples over stereo samples?
Mono samples take up less RAM in the sampler and doubles the amount of sampling time available
15 - What MIDI control messages can a typical sampler read?
Sampler is seen as a slave to a computer DAW controlled in real time via MIDI. Sampler must be set to ’external MIDI sync’. MIDI controllers can be either a ‘continuous’ controller like a pitch bend, or simply ‘on or off’ messages for keys (note on note off/velocity) and switches (bank select/program change)
MIDI clock messages control the tempo of the sampler.
Start, Stop and continue messages, Song position pointer (SPP) and Song select messages let sampler know when and where to play.
16 - How can an instrument with a long sustain be created from an instrument with a short sustain using a sampler?
Looping of the sample is required. Most sustained sounds have an initial attack sound and as it starts to decay it becomes consistent and little about the sound changes. Looping the middle part of the sample creates a sustained effect. Doesn’t work for short percussive sounds.
17 - Aside from a MIDI lead, what other connections are (or can be) made from a hardware sampler?
SCSI, USB and firewire to connect HARD DRIVE/CD ROM/FLOPPY/ZIP DRIVE/COMPUTER
Balanced/Unbalanced analogue I/o
Optical digital I/o (S/PDIF)
Word clock
Headphone jack
18 - How does a hardware sampler ensure that there is no latency?
All samples are loaded into hardware sampler’s RAM which gives zero latency when playing back on demand
19 - How can sample looping be used to save storage space?
A small looped section of a sample gives the impression of a sustained sample without having to play back the whole sound required. This technique frees up storage space. Envelope shapers can be used to modify envelope of looped sample. Good for creating a natural decay and stops sound ending abruptly when key is released
20 - What are the main requirements of a glitch free loop?
Waveform shapes at start and end of loop must be equal in level, shape and phase.
21 - Why are closed and open hi-hats often sent to the same mute group?
They are usually recorded on the same channel/microphone as they come from the same instrument
22 - On hardware samplers, how much sample time would you typically get out of 64MB storage?
A sample at 44.1KHz with 64MB of storage would give approximately 12 minutes of playback
23 - How might you achieve a chorus effect using a sampler that does not have an effects section?
Assigning multiple samples of the same sound to keys next to each other on the keyboard. This will give a chorus effect when played together as the samples are detuned from each other.
24 - How might you soften the start of a drum sample (single hit)?
An envelope generator can be used to elongate the attack time reducing any harshness. Different envelopes can be activated by assigning velocity control messages to 2 or more generators.
25 - In which phase(s) of the envelope (attack/decay/sustain/release) might you place the loop in a sample?
Mainly the sustain as it is a continuous part of the waveform holding at the same amplitude. Looping the release creates a delay effect.
You can use different samples for the attack and sustain portions of a sound, cross fading between sustained sounds by routing the LFOs to the sample level and filter cut-off frequency.
26 - Describe the differences in sound between a multi-sampled piano and a real piano.
A sample of a piano will only sound natural over a couple of semitones either side of the route key. This zone on the keyboard is known as a ‘key group’. More key groups will require more memory but will produce a more accurate sound.
Key velocity is also a factor in determining the timbre of a sound. Multi samples must be made across both pitch and force. Samples are taken only one note at a time. A real life piano produces a sonic blend of harmonics/harmonies when notes are played at the same time.
27 - State the two main criteria for the successful looping of a single sampled note that is consistent in level and harmonic content.
The phase of the start and end points must match and both must be at the zero crossing point
http://www.fortunecity.com/emachines/e11/86/synth7.html
http://www.sounduser.com/articles/begin.html
http://www.soundonsound.com/sos/1995_articles/oct95/midibasics3.html
http://www.djmixsource.com/multisampling1.htm
http://www.samplecraze.com/tutorial.php?xTutorialID=8
http://www.midiguy.com/MGuy/MQSampler/MQSampler.html
http://hem.passagen.se/tkolb/art/synth/samp_e.htm
http://www.soundonsound.com/sos/1996_articles/jan96/samplebasics1.html
http://www.mpc-samples.com/tutorial.php?xTutorialID=8
http://reviews.sonikmatter.com/native_instruments/kontakt.php
http://groups.yahoo.com/group/exs-users/message/10289 |
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Sat Oct 08, 2005 3:01 pm |
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tobyh1000
Joined: 10 Jul 2005
Posts: 13
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Sampling 1 – Week 6
sorry its late-couldn't get on to the webpage yesterday.
01- What are the logistical disadvantages of multisampling?
Takes a long time to record samples and if you don’t record every possible octave in every key the sampler is left to change the pitch itself- where the quality would be far worse than if recorded directly.
02- What is the importance of 'zero crossing' with sampled material?
Zero crossing is the point where the signal changes from positive/negative to negative/positive and its importance lies in with sampled material that is best to loop samples at these zero crossing points to reduce glitches in the sound quality.
03 - What problems may there be with sampled material from vinyl in terms of pitch/tempo?
Depending on the quality of the vinyl and vinyl player the pitch and tempo will vary, for instance is the vinyl is warped, the tempo will speed up at points resulting in a higher pitch- therefore not allowing quality samples to be recorded.
04 - What are the benefits of multisampling?
Multisampling allows the regeneration of real instruments through the use of samples at any key or pitch and octave, this is the main benefit along with its easy of use once recorded through multisampling.
05 - What are the advantages of USB connectivity for a sampler?
Allows easy plug and play connectivity. Can record straight to computer hard disk which allows mass storage for samples. Can then allow computer editing of samples directly through various programs.
06 - Why do some samplers offer SCSI connectivity?
To allow fast data connection to and from the computer and sampler, and also to allow cd-rom access, for writing of samples.
07 - What is 'tracking'?
When the frequency of the note is increased with the cut off frequencies also increased to allow a more realistic sound.
08 - Why might an LFO be used with a sample?
To change the modulation of the sample.
09 - What filters are commonly offered with contemporary samplers?
High pass, low pass and band pass filters.
10 - How do 'soft samplers' such as Gigasampler store their samples?
On a hard disk.
11 - Why are Zip Drives used with some hardware samplers?
Good for backups, cheap and good size alternative to hard disk.
12 - How can a sampler be used to add a 'vinyl effect' to a song?
A sampler could record a loop of the vinyl cracking off and create a sample, which could be played along side other tracks to create the illusion of vinyl effect.
13 - What benefits do samplers with multiple physical outputs have?
The benefits multiple output samplers give are the capability to provide output of specific samples as tracks, to inputs in a mixer to allow effects to be added.
14 - What are the benefits of working with mono samples over stereo samples?
The benefits of working with mono samples over stereo samples are that with mono samples, the quality is less than stereo and therefore requires less space for storage in memory, and is double the length of any samples recorded comparatively. Also easier to use within a mixer as both the left and right channel will appear exactly the same.
15 - What MIDI control messages can a typical sampler read?
The midi control messages that a typical sampler can read are note on or off, program change and bank select.
16 - How can an instrument with a long sustain be created from an instrument with a short sustain using a sampler?
17 - Aside from a MIDI lead, what other connections are (or can be) made from a hardware sampler?
Other connections can be made by SCSI, USB, analogue in/out, digital in/out, S/PDIF in/out.
18 - How does a hardware sampler ensure that there is no latency?
The hardware sampler stores samples in the RAM, and when loaded from the RAM there is no latency.
19 - How can sample looping be used to save storage space?
Using sample looping saves storage space by instead of sampling the same sound separately everytime it is needed; creating lots of samples and therefore taking up more space, you can use just looping and just have one sample instead.
20 - What are the main requirements of a glitch free loop?
The main requirements of a glitch free loop are making sure the beginning and end of the loop is equal, through such variables of level, shape and phase.
21 - Why are closed and open hi-hats often sent to the same mute group?
If closed and open hi-hats are sent to the same mute group only one will be played at one time. This is ok because they are not supposed to be played together.
22 - On hardware samplers, how much sampletime would you typically get out of 64MB storage?
As Freq. Rate x bits per sample/8 = Bytes per second
And Bytes per second x 60 = Mono file size per minute in MB
And 2 x mono file size per minute in MB = Stereo file size per minute in megabytes.
And Storage space in megabytes / Megabytes per minute (mono file) = Minutes of sample time
So 44.100 x 16/8 = 88.2 Bytes per second
88.2 x 60 = 5.292 MB per min
2 x 5.292 = 10.584 MB per min
so 64MB/10.584MB = 6.046 mins of sampletime.
23 - How might you achieve a chorus effect using a sampler that does not have an effects section?
To achieve a chorus effect you need to modulate a sample using a LFO out of synch with the same sample played simultaneously.
24 - How might you soften the start of a drum sample (single hit)?
To soften the start of a drum hit you could increased the attack time wirhin the ADSR envelope.
25 - In which phase(s) of the envelope (attack/decay/sustain/release) might you place the loop in a sample?
In the sustain phase of the envelope.
26 - Describe the differences in sound between a multi-sampled piano and a real piano.
With a multisampled piano you may not get the same ADSR as a real piano, as is dependant on how it is played –i.e. how hard the piano keys are pressed. It may sound very close but never quite reaching perfection.
27 - State the two main criteria for the successful looping of a single sampled note that is consistent in level and harmonic content.
Seamless looping is required, so no empty gaps at start or end of the sample. Also the effects over the sample, if any, need to be consistent throughout the sample unless applied equally over the waveform, so it goes unnoticed for errors. |
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Sun Oct 09, 2005 7:34 am |
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