ben m
Joined: 15 Sep 2002
Posts: 337
Location: UK |
| Week 8 - MIDI |
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A shed-load of questions this week - sock it to me!
01 - What does MIDI stand for?
02 - Is MIDI a serial or parallel data flow?
03 - How does MIDI data contain timing information?
04 - What are the advantages and disadvantages of MIDI over digital audio?
05 - Briefly describe the General MIDI standard
06 - What other standards have evolved from GM?
07 - What is the data rate of MIDI information in kbits?
08 - What is a UART?
09 - What purpose does a MIDI Thru connection serve?
10 - What is daisy-chaining in terms of MIDI connectivity, and what are its
disadvantages?
11 - What are the advantages of multi-port MIDI interfaces?
12 - What is a MIDI channel?
13 - With reference to the MIDI interface and the MIDI specification explain why MIDI systems can only have 16 channels?
14 - What channel must be used for drums/percussion under the GM standard?
15 - What does Omni mean in terms of the reception of MIDI information on discrete channels?
16 - What is the status byte and what information will it typically include?
17 - What information is typically found in the data byte?
18 - Describe the three bytes of a MIDI note-on message.
19 - What are control change (cc) messages?
20 - What is the purpose of system exclusive (sysex) messages?
21 - What is the difference between channel and system messages?
22 - What MIDI note number is the musical note C3 on a MIDI keyboard?
23 - How may velocity values are there?
24 - What is 'running status'?
25 - In running status, why is a velocity value of 0 treated as a note off message?
26 - What is the purpose of the 'Local' setting on MIDI devices?
27 - What are system realtime messages?
28 - What are Song position pointers (SPPs)?
29 - Briefly describe the MIDI TimeCode (MTC) protocol.
30 - Briefly describe the MIDI Machine Control (MMC) protocol.
31 - Why are modulation wheels often found on MIDI keyboards?
32 - Define the term polyphony.
33 - Define the term multi-timbral
34 - What is aftertouch?
35 - What features do mixing consoles offer that can be controlled by MIDI?
36 - How do MIDI messages such as modulation, expression attempt to recreate the nuances of 'real instruments'?
37 - List eight types of MIDI message which are either System Common or System Real Time. (Hint: these are messages that are NOT identified by MIDI Channel numbers).
38 - List four synchronisation strategies used in MIDI music production that can be used, with appropriate equipment, to synchronise a MIDI sequencer and a multitrack audio recorder. Expand any abbreviations.
39 - MIDI timecode quarter-frame, song position pointer, song select, tune request and end of exclusive are all what type of MIDI message?
40 - What does the first bit of each byte of a MIDI message signify?
41 - Explain the relationship of sequencer tracks, MIDI channels and synthesiser voices.
42 - In a MIDI set up using a MIDI keyboard controller and a computer sequencer what methods may you be able to use to physically input MIDI control data? Give three.
43 - You have a cable with a 5-pin DIN connector at each end. If it is suitable for copying a recording from one cassette deck to another, would it be suitable for MIDI?
44 - What data is provided by a MIDI THRU connector?
45 - What would you be most likely to use the MIDI OUT connector for on a keyboardless MIDI sound module
46 - You are using a MIDI sequencer to record many complex tracks to be played on a MIDI system where several modules are chained together, THRU to IN. What might happen if you use Pitch Bend or Control Change messages excessively?
47 - Some MIDI equipment processes data from the IN connector before sending it to the THRU. What effect does this have on timing?
48 - You are mixing MTC on the same cable as musical data. How might this affect the timing of notes?
49 - You have connected a keyboard with 32 note polyphony to a sequencer and you find that it is only capable of 16 note polyphony when played manually. If the keyboard can give the full 32 notes when disconnected from the sequencer what has happened?
50 - You are recording a melody into a sequencer. The melody contains a complex series of notes and pitch bend movements and you can’t get both the notes and pitch bend moves right simultaneously. What should you do?
51 - You have recorded a piano sound into a sequencer performed by a keyboard player who tends to use the sustain pedal a lot. What problem might you find if you record another piano part on the same MIDI channel?
52 - You have sampled a four bar drum loop and you trigger it from the sequencer on the first beat of bar 1. You also trigger it on the first beat of bar 5. What will happen if you play the sequence from bar 3?
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ben@audiocourses.com |
Tue Apr 27, 2004 6:02 am |
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hoggs33
Joined: 09 Feb 2004
Posts: 55
Location: Nottingham, England |
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01 - What does MIDI stand for?
Musical Instrument Digital Interface.
02 - Is MIDI a serial or parallel data flow?
Serial
03 - How does MIDI data contain timing information?
Midi Timecode (MTC) uses SMPTE/EBU timecode adapted for use in a MIDI system. This time code normally used in film and television identifies each frame of a video recording ith a unique number in terms of hours, minutes, seconds and frames. This is called the address. It also contains a clock pulse so that the running speed of two pieces of equipment can be compared and controlled so that they always run in sync. MTC uses the address part on SMPTE/EBU timecode, but not the clock. MTC messages are sent four times per notional video frame, at a constant, non-tempo related rate and eight are required to build up a complete frame address.
04 - What are the advantages and disadvantages of MIDI over digital audio?
MIDI allows easy editing and it is possible to change the recorded sound without having to re-record the part so different sound can be tried out or even be used to trigger different instruments. It should be easily ‘transportable’ between different systems as it is a universal language. File sizes would be smaller also.
Digital Audio will usually have a more ‘real’ feel to it
05 - Briefly describe the General MIDI standard
General MIDI seeks to impose a standard set up of instruments so that any GM instrument has the same sounds appearing on the same program numbers, and the same drum sounds, appearing on the same keys – therefore a MIDI sequence created on one system would sound almost the same on a different system if that used General MIDI>
06 - What other standards have evolved from GM?
Yamaha XG and Roland GS?
07 - What is the data rate of MIDI information in kbits?
Each MIDI byte takes around one millisecond to transmit
08 - What is a UART?
Universal Asynchronous Receiver/Transmitter. – it handles conversions from a serial byte stream to a parallel byte stream and vice versa as required.
09 - What purpose does a MIDI Thru connection serve?
The Thru connection transmits an exact and near instantaneous copy of the data present on the In connector.
10 - What is daisy-chaining in terms of MIDI connectivity, and what are its
disadvantages?
Daisy chaining is when a number of instruments or ‘appliances’ are connected together by using the Out connection of the master then going to the In of the first part of the chain with another connector going from the Thru connection of this part of the chain and into the In of the next part etc.
The daisy chain has two disadvantages – firstly, if there is a fault on one cable or one module, then all module further downstream would cease to sounde. Secondly each module ill contribute to a delay in transmission of data. The dealy may be very small but can be perceptible in some circumstances.
11 - What are the advantages of multi-port MIDI interfaces?
Each MIDI device can have its own direct connection thus avoiding daisy chaining and the potential problems associated with that as referred to above.
12 - What is a MIDI channel?
MIDI allows multiple channels of data to be transmitted through a single cable. Up to 16 channels can be transmitted through a single cable. These 16 channels are referred to as MIDI channels – each carrying its own separate data.
13 - With reference to the MIDI interface and the MIDI specification explain why MIDI systems can only have 16 channels?
A channel is defined by a 4 bit code, which is encoded in binary so there are only 16 possible variations, hence only 16 channels.
14 - What channel must be used for drums/percussion under the GM standard?
10
15 - What does Omni mean in terms of the reception of MIDI information on discrete channels?
Omni means that an instrument will respond to all MIDI channels.
16 - What is the status byte and what information will it typically include?
The status byte is transmitted for each note that is played and it tells the instrument that a MIDI note is being transmitted for a particular channel.
17 - What information is typically found in the data byte?
The note number and velocity information.
18 - Describe the three bytes of a MIDI note-on message.
Each key press generates a Note-on message which contains the note number and its velocity.
19 - What are control change (cc) messages?
MIDI controllers are used to replicate the vast range of expressive capabilities of traditional instruments, which would otherwise be lacking if only note number, velocity and aftertouch were available. MIDI control messages therefore contain ‘additional’ information that shape and fine fine tune a sound such as balance, expression, panning etc.
20 - What is the purpose of system exclusive (sysex) messages?
These can be used to send data such as patch parameters or sample data between MIDI devices. MIDI equipment manufacturers can define their own format for sysex data.
21 - What is the difference between channel and system messages?
Channel messages are channel specific and include the channel number in their status byte. System messages are system wide, not addressed to specific channels.
22 - What MIDI note number is the musical note C3 on a MIDI keyboard?
60
23 - How may velocity values are there?
128
24 - What is 'running status'?
As each MIDI byte takes around one millisecond to transmit, if for example six notes were played simultaneously, the time taken between the first and last note would be 18 milliseconds which would be noticeable and produces a ‘flamming’ effect. Part of the problem is that for each note a status byte has to be transmitted saying that a MIDI note is being transmitted for a particular channel. Then two data bytes follow with the actual note number and velocity. Running status allows only the first status byte to be transmitted, and the receiving equipment will assume that all the subsequent messages are of the same type and channel, until another status byte says otherwise. This allows savings of up to almost 33% in data transmission.
25 - In running status, why is a velocity value of 0 treated as a note off message?
The drawback initially with running status was that each note-on message had an associated note-off, which of course is a different status. In the worst case of a sequence of single notes, running status would have no benefit at all. To get round this, a note-on message with velocity zero was designed as an alternative way of sending a note-off message.
26 - What is the purpose of the 'Local' setting on MIDI devices?
The local setting enables the sound of an instrument itself to be played directly as opposed to through a MIDI sequencer.
27 - What are system realtime messages?
These messages are used for timing and real time control of certain devices on the MIDI bus.
28 - What are Song position pointers (SPPs)?
These are pointer within a song that allows playback to start from any of the pointers rather than going back to the beginning of the song.
]
29 - Briefly describe the MIDI TimeCode (MTC) protocol.
Think I pretty much covered this in question 3.
30 - Briefly describe the MIDI Machine Control (MMC) protocol.
Compared to a MIDI sequencer, a tape recorder (analog or digital) is very slow to respond - you have to wind tape to get where you want to go. Also, it is easy for a MIDI sequencer to act as a slave in a synchronized system. So if you wanted to combine multitrack tape and a MIDI sequencer in your system, then the sequencer would have to be the slave because the multitrack nearly always demands to be the master.
There is a solution to this in the form of MIDI Machine Control (MMC). A tape recorder that is MMC-capable can accept transport commands over MIDI. So you could press play on the sequencer, and it would issue a play command to the multitrack. It could even issue a command to locate to a certain point on the tape. Once the tape starts playing, the multitrack sends timecode back to the sequencer, which would be MTC or SMPTE/EBU in the form of LTC converted to MTC. The sequencer will then act as the slave.
31 - Why are modulation wheels often found on MIDI keyboards?
They allow real-time control of expression from the keyboard by transmitting control change messages.
32 - Define the term polyphony.
The ability to be able to play more than one note at a time – for example a 16 note polyphonic keyboard could play up to 16 notes at the same time.
33 - Define the term multi-timbral
The ability to play more than one sound at a time.
34 - What is aftertouch?
Aftertouch is the ability for a keyboard to respond to further pressure on the key once it is pressed down.
35 - What features do mixing consoles offer that can be controlled by MIDI?
Things such as automation, mutes, VCA control, start and stop info etc.
36 - How do MIDI messages such as modulation, expression attempt to recreate the nuances of 'real instruments'?
By enabling effects such as pitch bend and vibrato
37 - List eight types of MIDI message which are either System Common or System Real Time. (Hint: these are messages that are NOT identified by MIDI Channel numbers).
Song position
Song select
Tune request
System reset
Active sensing
MIDI clock
All notes off
Program change
38 - List four synchronisation strategies used in MIDI music production that can be used, with appropriate equipment, to synchronise a MIDI sequencer and a multitrack audio recorder. Expand any abbreviations.
MT (MIDI Time Code)
SMPTE/EBU (Society of Motion Picture and Television Engineers/European Broadcasting Union)
MMC (MIDI Machine Code)
39 - MIDI timecode quarter-frame, song position pointer, song select, tune request and end of exclusive are all what type of MIDI message?
System real time messages.
40 - What does the first bit of each byte of a MIDI message signify?
It identifies the type of MIDI message – i.e whether it is a status byte or a data byte.
41 - Explain the relationship of sequencer tracks, MIDI channels and synthesiser voices.
Each sequencer track will have16 MIDI channels and can hold MIDI data to play 16 voices.
42 - In a MIDI set up using a MIDI keyboard controller and a computer sequencer what methods may you be able to use to physically input MIDI control data? Give three.
Via USB, the MIDI interface of the computers built in soundcard (MPU-401) or standard MIDI connectors on a sound card. Possibly by a firewire interface also.
43 - You have a cable with a 5-pin DIN connector at each end. If it is suitable for copying a recording from one cassette deck to another, would it be suitable for MIDI?
No because out of the 5 pins, 1 and 3 are not used to transfer MIDI.
44 - What data is provided by a MIDI THRU connector?
The same data that was input from a MIDI In connector.
45 - What would you be most likely to use the MIDI OUT connector for on a keyboardless MIDI sound module
Bulk Data Dumps.
46 - You are using a MIDI sequencer to record many complex tracks to be played on a MIDI system where several modules are chained together, THRU to IN. What might happen if you use Pitch Bend or Control Change messages excessively?
This could increase the latency and cause playback problems with opos and glitches due to the amount of additional data being transferred.
47 - Some MIDI equipment processes data from the IN connector before sending it to the THRU. What effect does this have on timing?
This could result in timing dealyad/latency.
48 - You are mixing MTC on the same cable as musical data. How might this affect the timing of notes?
This may cause the note timing to become unstable resulting in dealys in the timing.
49 - You have connected a keyboard with 32 note polyphony to a sequencer and you find that it is only capable of 16 note polyphony when played manually. If the keyboard can give the full 32 notes when disconnected from the sequencer what has happened?
Not entirely sure but something to do with the notes being played twice or sent back twice.?
50 - You are recording a melody into a sequencer. The melody contains a complex series of notes and pitch bend movements and you can’t get both the notes and pitch bend moves right simultaneously. What should you do?
Record then separately – i.e record the melody first and the the pitch bend after.
51 - You have recorded a piano sound into a sequencer performed by a keyboard player who tends to use the sustain pedal a lot. What problem might you find if you record another piano part on the same MIDI channel?
The sustain pedal info that was recorded would affect the second piano part also.
52 - You have sampled a four bar drum loop and you trigger it from the sequencer on the first beat of bar 1. You also trigger it on the first beat of bar 5. What will happen if you play the sequence from bar 3?
It may not loop correctly or the first triggered loop may still be playing ‘underneath’ the trigger at bar 3. |
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Thu Apr 29, 2004 8:38 pm |
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iNSTiNCT2765
Joined: 05 Nov 2003
Posts: 60
Location: Denmark |
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Week 8 - MIDI
01 - What does MIDI stand for?
MIDI stands for Musical Instrument Digital Interface
02 - Is MIDI a serial or parallel data flow?
MIDI is a serial interface with serial data flow.
03 - How does MIDI data contain timing information?
MIDI data contains timing information using MIDI Clock messages. The Clock messages are sent from the master device to the connected slave device(s) and run at a rate of 24 pulses per quarter note.
04 - What are the advantages and disadvantages of MIDI over digital audio?
MIDI files are a lot smaller than audio files due to the fact that they don’t contain the actual sounds but the composition of them. This makes it easy to move between devices and could also mean that you can compose something on a computer with a really bad sounding MIDI soundcard and transfer it to a studio computer connected to a sound module and re-produce a more realistic sound. Midi information is also easy to change (i.e. replaying a part to make it tighter or moving an out of tune up or down). This is not possible with digital audio.
Having a lot of MIDI channels with all the messages and notes could make it really confusing and if everything is sounding good then it would probably be smart to record the tracks to audio for final mixing.
05 - Briefly describe the General MIDI standard
The GM standard was developed in 1991 and is a way of making different tone generators compatible in the sense that a MIDI composition made on one is going to play using the same voices on the next.
06 - What other standards have evolved from GM?
Two other standards that have evolved from GM are General Standard (GS) and Yamaha XG. The GS offers more controllers and sounds than the GM standard. The Yamaha XG standard enhances the musical experience by adding more voices, voice editing capabilities, effects and external input.
07 - What is the data rate of MIDI information in kbits?
MIDI data flows at a rate of 31.25 kbits per second.
08 - What is a UART?
UART stands for Universal Asynchronous Receiver Transmitter and is a computer component that handles asynchronous serial communication and manages the serial ports.
09 - What purpose does a MIDI Thru connection serve?
It carries out a duplicate of the MIDI messages received through the IN connection on a device.
10 - What is daisy-chaining in terms of MIDI connectivity, and what are its disadvantages?
Daisy-chaining in terms of connecting MIDI is when multiple devices are connected to each other one after another. For example, the MIDI OUT from a keyboard is connected to the MIDI IN on a sampler. Then the MIDI THRU on the sampler is connected to the MIDI IN on a synthesizer. Then the MIDI THRU on the synth is connected to the MIDI THRU on another synth and so on. The disadvantage of this set up is that MIDI messages generated on the keyboard are then sent to all connected devices and affect them all equally meaning you still only have 16 MIDI channels to share between all connected devices. So if you are playing a loop from the sampler on MIDI channel one and don’t want anything else to sound, then the volume on anything on channel one on the other connected devices must be turn down fully. Now channel one is not available for use on any of the other devices. Another disadvantage is that all devices that come before the device you want to generate the sound have to be turned on in order for the MIDI messages from the keyboard (first link in the chain) to reach the device. Using the keyboard -> sampler -> synth1 -> synth2 example, in order for the MIDI messages from the keyboard to reach synth2, the sampler and synth1 have to be turned on as well.
11 - What are the advantages of multi-port MIDI interfaces?
The advantages of multi-port MIDI interfaces are that multiple MIDI devices can be connected to the interface and 16 MIDI channels would be available to each of them exclusively without having to share with other devices like in daisy-chaining. The interface would also offer better synchronisation between the connected devices.
12 - What is a MIDI channel?
A MIDI channel is one of 16 control channels that independently control a MIDI device.
13 - With reference to the MIDI interface and the MIDI specification explain why MIDI systems can only have 16 channels?
14 - What channel must be used for drums/percussion under the GM standard?
Channel 10 is used for drums and percussion under the GM standard.
15 - What does Omni mean in terms of the reception of MIDI information on discrete channels?
Omni means that the MIDI device doesn’t respond to just one but all 16 channels.
16 - What is the status byte and what information will it typically include?
The status byte contains the MIDI message that determines what function is going to be executed like:
8 Note-Off
9 Note-On
A Aftertouch
B Control Change
C Program Change
D Channel Pressure
E Pitch Wheel
17 - What information is typically found in the data byte?
The note and the velocity of it.
18 - Describe the three bytes of a MIDI note-on message.
The first byte is the status byte and would contain the note-on number (9) followed by the MIDI channel number (n). The second byte is a data byte that holds the note number and letter (kk) for example the middle C would be 3C. The last byte determines the velocity of the note (vv). So a MIDI note-on message would look something like this:
9n kk vv
19 - What are control change (cc) messages?
Control change messages are messages that control a variety of functions including panning and volume. They only affect the channel that is indicated in the status byte.
20 - What is the purpose of system exclusive (sysex) messages?
Sysex messages are used to send patch parameters and sample data. This is the only type of message that is more than a few bytes long. This can be used to upgrade the device OS.
21 - What is the difference between channel and system messages?
A channel message only affects the specified MIDI channel while system messages affect the entire device and are not associated with a MIDI channel.
22 - What MIDI note number is the musical note C3 on a MIDI keyboard?
The musical note C3 corresponds to MIDI note number 60.
23 - How many velocity values are there?
Including 0 there are 128 velocity values (0-127).
24 - What is 'running status'?
To reduce the amount of data sent when transmitting MIDI messages, when messages with the same status byte are triggered at the same time, only one status byte needs to be transmitted. The status byte is only sent with the first message and not the subsequent ones, which only send data bytes. This is called ‘running status’. It only works with Channel Voice and Channel Mode messages like Note-On.
25 - In running status, why is a velocity value of 0 treated as a note off message?
This adds to the effectiveness of the ‘running status’ concept of data reduction because instead of having to transmit two status bytes, one for Note-On and another for Note-Off, only one status byte is transmitted due to the fact that the Note-On value 0 (off; no sound) is of the same status byte as any Note-On value used to turn the note on. No ‘release velocity’ can be transmitted using this concept.
26 - What is the purpose of the 'Local' setting on MIDI devices?
The ‘Local’ setting on MIDI devices, such as synthesizers or sound modules, allows you to manipulate the sound using the knobs available on the rack.
27 - What are system real-time messages?
System real-time messages are used by the sequencer to regulate and synchronise timing. They consist only of a status-byte and no data-bytes.
28 - What are Song position pointers (SPPs)?
SPP’s are two data bytes sent from the master MIDI device to the slave devices and determine the song position.
29 - Briefly describe the MIDI Time Code (MTC) protocol.
This protocol translates SMPTE Time Code to a time code that conforms to MIDI. It’s all about ‘real time’ and has nothing to do with tempo.
30 - Briefly describe the MIDI Machine Control (MMC) protocol.
MMC is designed to control hard disk recording systems and other playback and recording machines using a MIDI cable. This is done using Sysex messages.
31 - Why are modulation wheels often found on MIDI keyboards?
The modulation wheel gives you real-time access to pitch bending while recording MIDI.
32 - Define the term polyphony.
The number of notes that can sound simultaneously is determined by the amount of polyphony. (16 note polyphony means 16 notes can be played at the same time.)
33 - Define the term multi-timbral
This means that more than one program can be played at once. This allows 16 different programs to be assigned to each of the 16 MIDI channels.
34 - What is aftertouch?
Aftertouch is the ability to still apply pressure to a key after it has been pressed down. The Aftertouch message conveys the amount of pressure applied at any given time.
35 - What features do mixing consoles offer that can be controlled by MIDI?
Features such as fader automation, mutes, effects sends and creative panning can be controlled by MIDI.
36 - How do MIDI messages such as modulation, expression attempt to recreate the nuances of 'real instruments'?
Modulation can add tremolo to a sound and by pitch bending a bass can give a nice live feel to it.
37 - List eight types of MIDI message, which are either System Common or System Real Time. (Hint: these are messages that are NOT identified by MIDI Channel numbers).
MTC
Song position pointer
Song select
Tune request
MIDI clock
Active sense
MIDI start
MIDI stop
38 - List four synchronisation strategies used in MIDI music production that can be used, with appropriate equipment, to synchronise a MIDI sequencer and a multitrack audio recorder. Expand any abbreviations.
MIDI Time Code
MIDI Machine Control
MIDI Clock
(Fourth)
39 - MIDI timecode quarter-frame, song position pointer, song select, tune request and end of exclusive are all what type of MIDI message?
They are all System Common messages.
40 - What does the first bit of each byte of a MIDI message signify?
41 - Explain the relationship of sequencer tracks, MIDI channels and synthesiser voices.
A sequencer can have many tracks that can each be assigned to any of the 16 MIDI channels of the connected synthesizer. If two tracks have been assigned to the same MIDI channel they will each play the same voice and MIDI channel messages from a keyboard will affect both of the tracks. For example, if you have played a bass loop on track one, which is assigned to MIDI channel 1, and have added some pitch bending, then if you play the bass on track two, which is also assigned to MIDI channel 1, the pitch bend will affect it in the same way.
42 - In a MIDI set up using a MIDI keyboard controller and a computer sequencer what methods may you be able to use to physically input MIDI control data? Give three.
You can input MIDI control data by playing the MIDI keyboard, by using the modulation and pitch bending features included on your keyboard or you can use the mouse connected to the computer.
43 - You have a cable with a 5-pin DIN connector at each end. If it is suitable for copying a recording from one cassette deck to another, would it be suitable for MIDI?
Yes, the cable would be suitable for MIDI, though pins 1 and 3 aren’t used.
44 - What data is provided by a MIDI THRU connector?
Same data that is received on the MIDI IN connector of the device.
45 - What would you be most likely to use the MIDI OUT connector for on a keyboardless MIDI sound module?
The MIDI OUT on the sound module would be connected to the MIDI IN on the MIDI interface so real-time knob changes that manipulate the sound could be recorded into the sequencer.
46 - You are using a MIDI sequencer to record many complex tracks to be played on a MIDI system where several modules are chained together, THRU to IN. What might happen if you use Pitch Bend or Control Change messages excessively?
This might cause a delay due to the increased internal processing going on in the devices before data is sent to the THRU connector.
47 - Some MIDI equipment processes data from the IN connector before sending it to the THRU. What effect does this have on timing?
The signal coming out through the THRU connector is going to have the delay time that the device takes to process the data internally affecting the next device in the daisy-chain in the sense that it might be playing with a slight delay.
48 - You are mixing MTC on the same cable as musical data. How might this affect the timing of notes?
If a MIDI cable is being used to its capacity with both MTC and other MIDI data, the MTC might arrive a little late and affect the timing of the notes. It is better to have a MIDI cable dedicated to MTC exclusively if you have a multi-port MIDI interface.
49 - You have connected a keyboard with 32-note polyphony to a sequencer and you find that it is only capable of 16-note polyphony when played manually. If the keyboard can give the full 32 notes when disconnected from the sequencer what has happened?
When a note is pressed on the keyboard, the MIDI message is sent to the sequencer to trigger that note, and then the message is sent back to the keyboard so it is triggered and the sound is generated. This means that the polyphony is cut in half.
50 - You are recording a melody into a sequencer. The melody contains a complex series of notes and pitch bend movements and you can’t get both the notes and pitch bend moves right simultaneously. What should you do?
You should record in the notes first and then play them back and then record in the complex pitch bend movements overtop of the same channel.
51 - You have recorded a piano sound into a sequencer performed by a keyboard player who tends to use the sustain pedal a lot. What problem might you find if you record another piano part on the same MIDI channel?
The sustain messages will also affect the second piano part if it is recorded on the same MIDI channel. If this is unwanted then load the same piano program to another timbre on the module and set it to an unused MIDI channel and record it onto it instead of the same channel as the first piano part.
52 - You have sampled a four bar drum loop and you trigger it from the sequencer on the first beat of bar 1. You also trigger it on the first beat of bar 5. What will happen if you play the sequence from bar 3?
The loop won’t sound until it reaches bar 5 because it isn’t being triggered at bar 3.
Last edited by iNSTiNCT2765 on Mon May 10, 2004 2:23 am; edited 1 time in total |
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Fri Apr 30, 2004 9:49 pm |
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griff505
Joined: 23 Feb 2004
Posts: 68
Location: Bristol |
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Tune Request
End of Exclusive (EOX)
01 - What does MIDI stand for?
Musical Instrument Digital Interface.
02 - Is MIDI a serial or parallel data flow?
Serial (the bits of data making up each byte are transferred one after another).
03 - How does MIDI data contain timing information?
MIDI data contains timing information in the form of the MIDI clock messages. Messages are sent 24 times per quarter note for note resolution. Advanced sequencers will also subdivide each MIDI clock twenty times for a resolution of 480 times per quarter note. If the tempo changes, the speed of the MIDI Timing Clock will pass at a faster rate, but the number of status bytes per quarter note will stay the same.
04 - What are the advantages and disadvantages of MIDI over digital audio?
- MIDI is a digital signal, it's very easy to interface electronic instruments to computers, and then manipulate the MIDI data on the computer with software. The musician never loses control over every single individual action that he made upon each instrument, from playing a particular note at a particular point, to pushing the sustain pedal at a certain time, etc. The data is all there, but it's put together in such a way that every single musical action can be easily examined and edited.
- It takes much more storage to digitize the audio output of an instrument than it does to record an instrument's MIDI messages. The sounds themselves are not stored, only the messages received from the MIDI controller.
- MIDI is limited to instruments and sound sources that accept a MIDI input, therefore digital audio is crucial to record signals from all other instruments and voices.
05 - Briefly describe the General MIDI standard.
General MIDI - A music industry standard ratified in 1991. It established a set of 128 synth, orchestral and percussion sounds so that GM files and Standard MIDI Files play back on any GM-compatible instrument with predictable results. They can all play at least 16 sounds at once, and have at least 24-note polyphony. Before the GM standard was introduced, different synthesizers seldom had the same instrument on the same Patch Change (PC) number. When a MIDI file sequenced for a particular synthesizer was played back on a different synthesizer most, if not all the instruments would be wrong.
06 - What other standards have evolved from GM?
GS – Roland's General Synthesiser Standard (more controllers and sounds).
XG - Yamaha's MIDI extension (more voices, voice editing capability, effects, external input, and other features that contribute to enhanced musical expression).
07 - What is the data rate of MIDI information in kbits?
31.25 kbits =/- 1 per cent.
08 - What is a UART?
UART - Universal Asynchronous Receiver Transmitter - Used to route MIDI information to and from the automation computer, by generating and decoding serial data at the appropriate rate for the MIDI standard.
09 - What purpose does a MIDI Thru connection serve?
MIDI Thru allows MIDI devices to be ‘daisy-chained’ using the thru connector, whereby all subsequent devices receive information from the first device in the chain.
10 - What is daisy-chaining in terms of MIDI connectivity, and what are its
disadvantages?
Daisy chaining is the connecting of multiple MIDI devices. The controller will be connected to the MIDI-in of anther device from its MIDI-out. The MIDI-thru of the second device would be connected to the MIDI-in of another device, and so on. Each device can be set to receive data from specific MIDI channels, and the controller can be programmed to which device it is sending data to by setting the MIDI channel output on the controller.
Daisy chaining can cause latency problems depending on the length of the chain, and also the length of the chain can lead to problems setting up certain sounds to react only with certain data.
11 - What are the advantages of multi-port MIDI interfaces?
Multiport digital interfaces have a number of independent MIDI OUT ports. Up to 16 channels can be addressed by each of the MIDI OUTS, thus expanding the total number of channels addressable to 16 times the number of ports. Where such a system is used it common for each instrument to be connected to its own port, both in and out, which is especially useful with multi-timbral sound modules capable of operating on all 16 channels simultaneously. It also allows any instrument to be used as a controller, and makes it possible for instruments to send system exclusive information back to the computer without replugging. Multiport interfaces allow data received from more than one port to be merged, or allow recording from more than once source at a time
12 - What is a MIDI channel?
MIDI messages are made up of a number of bytes. Each part of the message has a specific purpose, and one of these is to define the receiving channel to which the message refers. In this way, a controlling device can make a message device specific – it can define which receiving instrument will act upon the data. There are 16 basic MIDI channels and instruments can be programmed to receive on a specific channel, or channels, or receive on all channels. The limit of 16 channels can be exceeded by using multiport MIDI interfaces.
13 - With reference to the MIDI interface and the MIDI specification explain why MIDI systems can only have 16 channels?
The channel tag consists of 4 bits in a MIDI channels status byte. Because this is encoded in binary, there are only 16 possibly variations, thus 16 channels.
14 - What channel must be used for drums/percussion under the GM standard?
Channel 10.
15 - What does Omni mean in terms of the reception of MIDI information on discrete channels?
If a MIDI device is set to Omni On, then the device will respond to information on all 16 channels.
16 - What is the status byte and what information will it typically include?
The status byte is the header message that is sent prior to the data byte. It holds information relating to the type of event that will follow and which channel it is targeted for.
17 - What information is typically found in the data byte?
Data bytes will, if needed, follow a status byte. They contain the information that further defines what the message is supposed to do. For example, if the MIDI message is Song Select, the data byte outlines the song number to change to.
18 - Describe the three bytes of a MIDI note-on message.
The first byte is the status byte, which indicates the event type and target channel. The second and third bytes indicate the note number and velocity.
19 - What are control change (cc) messages?
MIDI Control Change messages are used to control a wide variety of functions in a synthesizer. Control Change messages, like other MIDI channel messages, should only affect the channel number indicated in the status byte. The control change status byte is followed by one data byte indicating the "controller number", and a second byte which specifies the "control value". The controller number identifies which function of the synthesizer is to be controlled by the message.
For example, Controller Numbers 0 - 31 are generally used for sending data from switches, wheels, faders, or pedals on a MIDI controller device such as a musical instrument keyboard.
20 - What is the purpose of system exclusive (sysex) messages?
System Exclusive messages are used for more complex control and programming of synthesizers. System Exclusive messages can be used to control just about every facet of a synthesizer setup, for example, a single voice setup, a multi-voice setup or to change every voice on a synth at once. On some synths, they even allow you to perform the same functions as the control panel buttons. One problem with System Exclusive messages is that they cannot usually be used in real time, that is, while a piece is playing. Receiving System Exclusive messages often ties the synth up briefly causing a noticeable pause in the music.
21 - What is the difference between channel and system messages?
Channel messages are messages intended for one or more devices that respond to the information of the message assigned channel.
System messages concern all the devices in a MIDI setup.
22 - What MIDI note number is the musical note C3 on a MIDI keyboard?
60
23 - How may velocity values are there?
128
24 - What is 'running status'?
Running status is simply a clever scheme to maximize the efficiency of MIDI transmission (by removing extraneous Status bytes). The basic philosophy of running status is that a device must always remember the last Status byte that it received (except for Realtime), and if it doesn't receive a Status byte when expected (on subsequent messages), it should assume that it's dealing with a running status situation. A device that generates MIDI messages should always remember the last Status byte that it sent (except for Realtime), and if it needs to send another message with the same Status, the Status byte may be omitted.
25 - In running status, why is a velocity value of 0 treated as a note off message?
Note Off messages are broadcast as Note On with a velocity of 0, so that when playing series of notes, only one status byte needs to be sent.
26 - What is the purpose of the 'Local' setting on MIDI devices?
The local setting enables the sound of an instrument itself to be played directly as opposed to through a MIDI sequencer.
27 - What are system realtime messages?
Realtime messages are single-byte messages that can be sent anywhere in the data stream (without disrupting the current running status) that keep all connected devices in sync. They include commands like Start, Stop, Continue, and Timing Clock.
28 - What are Song position pointers (SPPs)?
A son position pointer is a system common message sent by a master device to control sequence playback. The master device sends this message to force a slave device to cue the playback to a certain point in the song/sequence. In other words, this message sets the device's "Song Position". The message doesn't actually start the playback. It just sets up the device to be "ready to play" at a particular point in the song.
29 - Briefly describe the MIDI Time Code (MTC) protocol.
MIDI Time Code was developed in order for electronic music studios, project studios and all other production environments to provide a cost-effective and easily implemented way to translate time code into time-stamped MIDI messages (and back). It allows SMPTE-based time code to be distributed throughout the MIDI chain to devices or instruments that are capable of understanding and executing MTC commands.
It is customary to separate MTC lines from MIDI cables that are communicating performance data. Only one master can exist within an MTC system, while any number of slaves can be assigned to follow, locate and chase to the master’s speed and position.
30 - Briefly describe the MIDI Machine Control (MMC) protocol.
MMC is a protocol developed to allow MIDI sequencers, hard disk recorders, tape and cideo transports and other recording systems to be remotely controlled from a hardware device or computer programme via MIDI. Specially designated system-exclusive messages are transmitted throughout the MIDI system to devices that can respond to MMC.
MMC control messages are able to communicate with individual devices within the connected network by assigning ID numbers to each relevant device. Any number of slaves can be assigned to one master controlling device or program.
31 - Why are modulation wheels often found on MIDI keyboards?
The modulation wheel sends Control Change (CC) messages to the connected device to allow for real time expression controls to be sent to the assigned parameter.
32 - Define the term polyphony.
Polyphony is a measure of how many notes of a MIDI voice can sound simultaneously. If an instrument has five note polyphony then you can play five distinct notes at the same time, a sixth simultaneous note would cause one of the others to stop sounding.
33 - Define the term multi-timbral
A multi- timbral sound module can play several parts on different channels simultaneously. A multi-timbral device is one that is prepared to sound like more than one instrument at a time. Each timbre will use one voice of polyphony.
34 - What is aftertouch?
A realtime control produced by pushing a key down further than the point at which the key's note sounds. Channel aftertouch affects all currently sounding notes; polyphonic aftertouch affects only the pressed note. Aftertouch is often routed to control vibrato, volume, and other parameters.
35 - What features do mixing consoles offer that can be controlled by MIDI?
Mixers that respond to MIDI can carry out functions ranging from control over mute functions and the creation of static snapshots for reconfiguration of user-defined mixer settings, to complete dynamic control over all mix functions.
36 - How do MIDI messages such as modulation, expression attempt to recreate the nuances of 'real instruments'?
Modulation can be used to control a synthesised sound in order to make it sound more like a ‘real’ instrument by allowing dynamic effects such as vibrato and pitch bend to be applied to the sound.
Modulation (controller #1) is generally used to control LFO depth, for effects like pitch vibrato. Vibrato can also be applied by other methods, such as aftertouch. Most synths respond to CC#1, and can have various functions assigned to respond to it.
Expression (controller #11) can be used to create crescendos and decrescendos, to expand and diminish intensity. The overall volume relations between different voices remain same, as expression controls the volume in percents scale.
37 - List eight types of MIDI message which are either System Common or System Real Time. (Hint: these are messages that are NOT identified by MIDI Channel numbers).
- MIDI Time Code (MTC)
- Song Position Pointer (SPP)
- Song Select Message
- Tune Request
- End of Exclusive (EOX)
- MIDI Clock
- System Reset
- Timing Clock
38 - List four synchronisation strategies used in MIDI music production that can be used, with appropriate equipment, to synchronise a MIDI sequencer and a multitrack audio recorder. Expand any abbreviations.
- MIDI Time Code - A MIDI interpretation of the traditional SMPTE protocol. Again this system requires that you create a tempo map.
- SMPTE/EBU - Society of Motion Picture and Television Engineers/European Broadcasting Union - Based on real time measured in hours, minutes and seconds, with further subdivisions to accommodate individual frames of TV and film material. Because SMPTE code is independent of tempo, a whole tape can be recorded or 'striped' with code before any recording or programming starts.
- FSK - Frequency Shift Keying - System records a series of electronic tones (output from a drum machine) onto a spare track of the tape machine. These tones are related to the tempo clock of the drum machine, so as the tempo is increased, the electronic sync track follows.
- MMC - MIDI Machine Code.
39 - MIDI timecode quarter-frame, song position pointer, song select, tune request and end of exclusive are all what type of MIDI message?
System real time messages.
40 - What does the first bit of each byte of a MIDI message signify?
The first byte of a MIDI message identifies the type of MIDI message - whether the byte is status or data byte 0 or 1.
41 - Explain the relationship of sequencer tracks, MIDI channels and synthesiser voices.
A sequencer can have as many tracks as the user specifies and the system can handle, each track will have 16 channels and can hold MIDI data to play 16 voices. Therefore a sequencer that had 8 tracks could play 128 voices.
42 - In a MIDI set up using a MIDI keyboard controller and a computer sequencer what methods may you be able to use to physically input MIDI control data? Give three.
MIDI control data input by playing the MIDI keyboard, by using the modulation and pitch bending features included on your keyboard or you can use the mouse connected to the computer.
43 - You have a cable with a 5-pin DIN connector at each end. If it is suitable for copying a recording from one cassette deck to another, would it be suitable for MIDI?
The cable would be suitable for MIDI although pins 1 and 3 would not be used,
44 - What data is provided by a MIDI THRU connector?
The MIDI Thru provides the same information as received by the MIDI in of the same device.
45 - What would you be most likely to use the MIDI OUT connector for on a keyboard-less MIDI sound module?
- Bulk data dumps.
- To transmit controller changes other than keyboard controls e.g. cut-off frequency.
46 - You are using a MIDI sequencer to record many complex tracks to be played on a MIDI system where several modules are chained together, THRU to IN. What might happen if you use Pitch Bend or Control Change messages excessively?
Latency could result from the amount of data being transferred.
47 - Some MIDI equipment processes data from the IN connector before sending it to the THRU. What effect does this have on timing?
This could also lead to latency problems if several daisy-chained devices all worked in this way,
48 - You are mixing MTC on the same cable as musical data. How might this affect the timing of notes?
As MTC takes priority over other MIDI messages (e.g. Note On/Off) the timing of notes may be inaccurate.
49 - You have connected a keyboard with 32 note polyphony to a sequencer and you find that it is only capable of 16 note polyphony when played manually. If the keyboard can give the full 32 notes when disconnected from the sequencer what has happened?
The sequencer has allowed MIDI thru to send the original data back to the keyboard and is thus triggering the notes twice. This will reduce the polyphony and normally make the keyboard sound out of phase.
50 - You are recording a melody into a sequencer. The melody contains a complex series of notes and pitch bend movements and you can’t get both the notes and pitch bend moves right simultaneously. What should you do?
First record the melody without pitch bends, then merge record the pitch bend movements.
51 - You have recorded a piano sound into a sequencer performed by a keyboard player who tends to use the sustain pedal a lot. What problem might you find if you record another piano part on the same MIDI channel?
The sustain pedal control change data will affect both piano parts.
52 - You have sampled a four bar drum loop and you trigger it from the sequencer on the first beat of bar 1. You also trigger it on the first beat of bar 5. What will happen if you play the sequence from bar 3?
The drum loops would only sound after bar 5. |
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Wed May 05, 2004 3:16 am |
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albertom
Joined: 21 Jan 2004
Posts: 22
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01 - What does MIDI stand for?
MIDI is an acronym for musical instrument digital interface
02 - Is MIDI a serial or parallel data flow?
Serial data flow.
Application software, such as Multimedia presentation packages, educational software, or games, sends MIDI data to the MIDI interface card in parallel form over the PC bus. The MIDI interface converts this information into serial MIDI data which is sent to the sound module.
03 - How does MIDI data contain timing information?
System Real Time Messages
The MIDI System Real Time messages are used to synchronize all of the MIDI clock-based equipment within a system, such as sequencers and drum machines. Most of the System Real Time messages are normally ignored by keyboard instruments and synthesizers. To help ensure accurate timing, System Real Time messages are given priority over other messages, and these single-byte messages may occur anywhere in the data stream (a Real Time message may appear between the status byte and data byte of some other MIDI message).
The System Real Time messages are the Timing Clock, Start, Continue, Stop, Active Sensing, and the System Reset message. The Timing Clock message is the master clock which sets the tempo for playback of a sequence. The Timing Clock message is sent 24 times per quarter note. The Start, Continue, and Stop messages are used to control playback of the sequence.
04 - What are the advantages and disadvantages of MIDI over digital audio?
MIDI vs. Digitized Audio
Originally developed to allow musicians to connect synthesizers together, the MIDI protocol is now finding widespread use as a delivery medium to replace or supplement digitized audio in games and multimedia applications. There are several advantages to generating sound with a MIDI synthesizer rather than using sampled audio from disk or CD-ROM. The first advantage is storage space. Data files used to store digitally sampled audio in PCM format (such as .WAV files) tend to be quite large. This is especially true for lengthy musical pieces captured in stereo using high sampling rates.
MIDI data files, on the other hand, are extremely small when compared with sampled audio files. For instance, files containing high quality stereo sampled audio require about 10 Mbytes of data per minute of sound, while a typical MIDI sequence might consume less than 10 Kbytes of data per minute of sound. This is because the MIDI file does not contain the sampled audio data, it contains only the instructions needed by a synthesizer to play the sounds. These instructions are in the form of MIDI messages, which instruct the synthesizer which sounds to use, which notes to play, and how loud to play each note. The actual sounds are then generated by the synthesizer.
For computers, the smaller file size also means that less of the PCs bandwidth is utilized in spooling this data out to the peripheral which is generating sound. Other advantages of utilizing MIDI to generate sounds include the ability to easily edit the music, and the ability to change the playback speed and the pitch or key of the sounds independently. This last point is particularly important in synthesis applications such as karaoke equipment, where the musical key and tempo of a song may be selected by the user.
05 - Briefly describe the General MIDI standard
The General MIDI (GM) Specification defines a set of general capabilities for General MIDI Instruments. The General MIDI Specification includes the definition of a General MIDI Sound Set (a patch map), a General MIDI Percussion map (mapping of percussion sounds to note numbers), and a set of General MIDI Performance capabilities (number of voices, types of MIDI messages recognized, etc.). A MIDI sequence which has been generated for use on a General MIDI Instrument should play correctly on any General MIDI synthesizer or sound module.
06 - What other standards have evolved from GM?
- General MIDI 2 or GM2. This is a set of extensions to GM1, increasing both the number of simultaneously available sounds (from 24 to 32) and the amount of control over editing and performance. Two channels (10 and 11) are devoted to percussions. All GM2 devices are backward compatible with GM1.
- General MIDI Lite or GML. That specification is intended for equipment that does not have the capability to support the full GM1 feature set (mobile applications).
- Scalable Polyphony MIDI Specification or SP-MIDI. This utilizes a new MIDI message that can be used to indicate how a MIDI data should be performed by devices with different polyphony. For example, music written for GM2's 32-note polyphony, could also be made to play on GM1 and GM Lite devices, by eliminating certain instrument parts according to the composer's choice.
07 - What is the data rate of MIDI information in kbits?
The MIDI data stream is a unidirectional asynchronous bit stream at 31.25 Kbits/sec. with 10 bits transmitted per byte (a start bit, 8 data bits, and one stop bit).
08 - What is a UART?
Universal Asynchronous Receiver / Transmitter. The fundamental function of a MIDI interface for the PC is to convert parallel data bytes from the PC data bus into the serial MIDI data format and vice versa (a UART function).
09 - What purpose does a MIDI Thru connection serve?
Information received on the MIDI IN connector of a MIDI device is transmitted back out (repeated) at the devices' MIDI THRU connector.
10 - What is daisy-chaining in terms of MIDI connectivity, and what are its
disadvantages?
Several MIDI sound modules can be daisy-chained by connecting the THRU output of one device to the IN connector of the next device downstream in the chain.
11 - What are the advantages of multi-port MIDI interfaces?
Multi-port MIDI interface, are two or more MIDI output sockets, each of which has its own set of MIDI channels. In order to make use of a multi-port interface, you have to use sequencing software that supports multi-port operation, but all the current market leaders (Steinberg, Emagic, MOTU, Opcode, and so on) have this facility. Within the software is a setup section that allows you to tell the system what type of interface you are using.
12 - What is a MIDI channel?
Is where a musical instrument can generally be set to transmit on MIDI messages. MIDI channel is a logical channel indicated by it's number and used to represent one instrument. 16 channels are available. Any MIDI instrument can be set to transmit on any one of these channels. Sound sources (synthesizers) are assigned channel numbers they respond to, multitimbral sound modules can listen to several channels at a time. Necessary sounds (patch numbers) are assigned to the channels. As a result, sending a note-on message to some channel is interpreted by the sound module as an instruction to play a note, using the instrument (sound) associated with the respective channel number.
13 - With reference to the MIDI interface and the MIDI specification explain why MIDI systems can only have 16 channels?
The single physical MIDI Channel is divided into 16 logical by the inclusion of a 4 bit Channel number within many of the MIDI messages. A musical instrument keyboard can generally be set to transmit on any one of the sixteen MIDI channels. A MIDI sound source, or sound module, can be set to receive on specific MIDI Channel(s).
MIDI messages utilizing the concept of channels include a 4-bit channel number in their status byte. By means of four bits, sixteen different values can be represented, from 0 to 15.
14 - What channel must be used for drums/percussion under the GM standard?
Channel 10.
15 - What does Omni mean in terms of the reception of MIDI information on discrete channels?
When Omni mode is turned on, the synthesizer will respond to incoming MIDI messages on all channels. Turning Omni mode off makes the synth to respond to only one channel.
16 - What is the status byte and what information will it typically include?
A MIDI message is made up of an eight-bit status. There are a number of different types of MIDI messages. Channel messages are those which apply to a specific Channel, and the Channel number is included in the status byte for these messages.
17 - What information is typically found in the data byte?
Channel Voice Messages are used to send musical performance information. The messages in this category are the Note On, Note Off, Polyphonic Key Pressure, Channel Pressure, Pitch Bend Change, Program Change, and the Control Change messages
18 - Describe the three bytes of a MIDI note-on message.
When a key is pressed on a MIDI keyboard instrument or MIDI keyboard controller, the keyboard sends a Note On message on the MIDI OUT port. The keyboard may be set to transmit on any one of the sixteen logical MIDI channels, and the status byte for the Note On message will indicate the selected Channel number. The Note On status byte is followed by two data bytes, which specify key number (indicating which key was pressed) and velocity (how hard the key was pressed).
19 - What are control change (cc) messages?
MIDI Control Change messages are used to control a wide variety of functions in a synthesizer. Control Change messages, like other MIDI Channel messages, should only affect the Channel number indicated in the status byte. The Control Change status byte is followed by one data byte indicating the "controller number", and a second byte which specifies the "control value". The controller number identifies which function of the synthesizer is to be controlled by the message.
20 - What is the purpose of system exclusive (sysex) messages?
System Exclusive messages can be used to send data such as patch parameters or sample data between MIDI devices.
21 - What is the difference between channel and system messages?
Channel messages are those which apply to a specific Channel, and the Channel number is included in the status byte for these messages. System messages are not Channel specific, and no Channel number is indicated in their status bytes.
22 - What MIDI note number is the musical note C3 on a MIDI keyboard?
60
23 - How may velocity values are there?
128 different velocity values ranging from 0 to 127 or 1 to 128.
24 - What is 'running status'?
MIDI data being sent from a sequencer can include a number of different parts. On a given beat, there may be a large number of musical events which should occur simultaneously, and the delays introduced by serialization of this information might be noticeable. To help reduce the amount of data transmitted in the MIDI data stream, a technique called "running status" may be employed.
Running status considers the fact that it is very common for a string of consecutive messages to be of the same message type. When running status is used, a status byte is sent for a message only when the message is not of the same type as the last message sent on the same Channel. The status byte for subsequent messages of the same type may be omitted (only the data bytes are sent for these subsequent messages).
25 - In running status, why is a velocity value of 0 treated as a note off message?
The key number is used in the receiving synthesizer to select which note should be played, and the velocity is normally used to control the amplitude of the note. When the key is released, the keyboard instrument or controller will send a Note Off message. The Note Off message also includes data bytes for the key number and for the velocity with which the key was released. The Note Off velocity information is normally ignored.
26 - What is the purpose of the 'Local' setting on MIDI devices?
There is an internal link between the keyboard and the sound module which may be enabled or disabled by setting the "local control" function of the instrument to ON or OFF respectively.
27 - What are system real time messages?
System Real Time messages are used for synchronization between clock-based MIDI components. System Exclusive messages include a Manufacturer's Identification (ID) code, and are used to transfer any number of data bytes in a format specified by the referenced manufacturer.
28 - What are Song position pointers (SPPs)?
The Song Position Pointer value is related to the number of MIDI clocks which would have elapsed between the beginning of the song and the desired point in the song. This message can only be used with equipment which recognizes MIDI System Real Time Messages (MIDI Sync).
29 - Briefly describe the MIDI Time Code (MTC) protocol.
The MTC Quarter Frame message is part of the MIDI Time Code information used for synchronization of MIDI equipment and other equipment, such as audio or video tape machines.
30 - Briefly describe the MIDI Machine Control (MMC) protocol.
MIDI Machine Control (MMC) is a protocol specifically designed to remotely control hard disk recording systems, and o|her machines used for record or playback, over a MIDI cable. The only way to do this is with System Exclusive messages, and so several specific SysEx messages were defined in order to implement MIDI Machine Control.
31- Why are modulation wheels often found on MIDI keyboards?
Vibrato and tremolo are effects which are often produced by musicians playing acoustic instruments. Vibrato is basically a low-frequency modulation of the pitch of a note, while tremolo is modulation of the amplitude of the sound. These effects are simulated in synthesizers by implementing low-frequency oscillators (LFOs) which are used to modulate the pitch or amplitude$of the synthesized sound being produced.
32 - Define the term polyphony.
The polyphony of a sound generator refers to its ability to play more than one note at a time. Polyphony is generally measured or specified as a number of notes or voices. Most of the early music synthesizers were monophonic, meaning that they could only play one note at a time. If you pressed five keys simultaneously on the keyboard of a monophonic synthesizer, you would only hear one note. Pressing five!keys on the keyboard of a synthesizer which was polyphonic with four voices of polyphony would, in general, produce four notes. If the keyboard had more voices (many modern sound modules have 16, 24, or 32 note polyphony), then you would hear all five of the notes.
33 - Define the term multi-timbral
A synthesizer or sound generator is said to be multitimbral if it is capable of producing two or more different instrument sounds simultaneously. If a synthesizer can play five notes simultaneously, and it can produce a piano sound and an acoustic bass sound at the same time, then it is multitimbral. With enough notes of polyphony and "parts" (multitimbral) a single synthesizer could produce the entire sound of a band or orchestra.
34 - What is aftertouch?
Some MIDI keyboard instruments have the ability to sense the amount of pressure which is being applied to the keys while they are depressed. This pressure information, commonly called "aftertouch", may be used to control some aspects of the sound produced by the synthesizer (vibrato, for example). If the keyboard has a pressure sensor for each key, then the resulting "polyphonic aftertouch" information would be sent in the form of Polyphonic Key Pressure messages. These messages include separate data bytes for key number and pressure amount. It is currently more common for keyboard instruments to sense only a single pressure level for the entire keyboard. This "Channel aftertouch" information is sent using the Channel Pressure message, which needs only one data byte to specify the pressure value.
35 - What features do mixing consoles offer that can be controlled by MIDI?
A lot of automating can be controlled by MIDI. For analogue consoles, this mostly means automated muting. Digital consoles are much more versatile in the automation sense, offering features like mix scene recalls or remote control of mix parameters. MIDI can be used for automix synchronization (through MTC messages) or for implementing a ‘fader start’ function. Bulk Dump function can be used for data transfer between consoles, or for backup either to a sequencer or to a MIDI data filer. A console can be used for controlling remote MIDI devices (eg to start/stop playback on a sequencer).
36 - How do MIDI messages such as modulation, expression attempt to recreate the nuances of 'real instruments'?
Modulation (controller #1) is generally used to control LFO depth, for effects like pitch vibrato. Vibrato can also be applied by other methods, such as aftertouch. Most synths respond to CC#1, and can have various functions assigned to respond to it. Assigning filter cutoff and/or resonance to respond to the modulation wheel makes basic timbral changes possible. Even more effect is achieved when VCA level can be simultaneously assigned to the same wheel; this enables imitative sounds to have a natural tonal change in sync with the volume variations.
Expression (controller #11) can be used to create crescendos and decrescendos, to expand and diminish intensity. The overall volume relations between different voices remain same, as expression controls the volume in percents scale.
37 - List eight types of MIDI message which are either System Common or System Real Time. (Hint: these are messages that are NOT identified by MIDI Channel numbers).
Song Select, MTC Quarter Frame, Song Position Pointer, Tune Request, End Of Exclusive, Timing Clock, Start, Continue, Stop, Active Sensing, System Reset
38 - List four synchronisation strategies used in MIDI music production that can be used, with appropriate equipment, to synchronise a MIDI sequencer and a multitrack audio recorder. Expand any abbreviations.
- FSK (Frequency Shift Keying) system records a series of electronic tones (output from a drum machine) onto a spare track of the tape machine. These tones are related to the tempo clock of the drum machine, so as the tempo is increased, the electronic sync track follows. To run the drum machine in sync with the tape machine, the tape output from the sync track is plugged into the Sync In socket on the drum machine, the drum machine switched to Tape Sync, and the tape started from the beginning. The drum machine will automatically start when it receives the sync code from the tape machine and should stay in time with the tape until you stop the tape machine.
- Smart FSK, a refinement of the original FSK sync code, still works by recording the code to tape in the form of tones. The advantages are that being designed to work with MIDI SPPs (Song Position Pointers), the tape machine can be started anywhere in the song and the sequencer will always find the right place.
- SMPTE (stands for the Society of Motion Picture and Television Engineers). SMPTE is based on real time measured in hours, minutes and seconds, with further subdivisions to accommodate individual frames of TV and film material. Because SMPTE code is independent of tempo, a whole tape can be recorded or 'striped' with code before any recording or programming starts. The starting tempo and the SMPTE location, plus any subsequent tempo changes, are stored in the form of a 'tempo map' which must be used alongside the sequencer data whenever the sequence is run sync'ed to tape.
- MTC (MIDI Time Code), essentially a MIDI interpretation of the traditional SMPTE protocol. Again this system requires that you create a tempo map.
39 - MIDI timecode quarter-frame, song position pointer, song select, tune request and end of exclusive are all what type of MIDI message?
System Common Messages
40 - What does the first bit of each byte of a MIDI message signify?
The first (most significant) bit of a byte indicates whether this is a status byte or a data byte. Status bytes have 1 on the first bit, while data bytes have 0. The first bit of a byte in MIDI data stream signifies the start of a byte data. MIDI data is transferred serially, using ten bits for every byte: a start bit, eight data bits and a stop bit.
41 - Explain the relationship of sequencer tracks, MIDI channels and synthesiser voices.
You generally devote each instrument sound you need a MIDI channel of it’s own. Each instruments’ performance is represented by MIDI Channel messages like note-on/note-off. You record the performance to a sequencer, individual MIDI channels being stored to different sequencer tracks. You then play back the MIDI sequence from a sequencer, here the MIDI channels correspond to voices on the synth. The instrument sound is chosen for each voice (MIDI channel) via a Program Change message.
42 - In a MIDI set up using a MIDI keyboard controller and a computer sequencer what methods may you be able to use to physically input MIDI control data? Give three.
A MIDI keyboard controller is used as an input device to a MIDI sequencer, and there are several sound modules connected to the sequencer's MIDI OUT port. A composer might utilize a system like this to write a piece of music consisting of several different parts, where each part is written for a different instrument.
The composer would play the individual parts on the keyboard one at a time, and these individual parts would be captured by the sequencer. The sequencer would then play the parts back together through the sound modules. Each part would be played on a different MIDI Channel, and the sound modules would be set to receive different channels.
A MIDI interface and the MIDI sound module might be combined on the PC add-in card. In fact, the Multimedia PC (MPC) Specification requires that all MPC systems include a music synthesizer, and the synthesizer is normally included on the audio adapter card (the "sound card") along with the MIDI interface function. Until recently, most PC sound cards included FM synthesizers with limited capabilities and marginal sound quality. With these systems, an external wavetable synthesizer module might be added to get better sound quality. Recently, more advanced sound cards have been appearing which include high quality wavetable music synthesizers on-board, or as a daughter-card options. With the increasing use of the MIDI protocol in PC applications, this trend is sure to continue.
43 - You have a cable with a 5-pin DIN connector at each end. If it is suitable for copying a recording from one cassette deck to another, would it be suitable for MIDI?
No. Ccable for cassette desks or stereo line uses pin 1 for left output/input, pin2 for screen, pin 3 for left input/output and pin 4&5 for right output/input. For MIDI pin 1 N/C, pin 2 screen, pin 3 N/C, pin 4 +5 volts and pin 5 MIDI data. They are not compatible.
44 - What data is provided by a MIDI THRU connector?
Information received on the MIDI IN connector of a MIDI device is transmitted back out (repeated) at the devices' MIDI THRU connector.
45 - What would you be most likely to use the MIDI OUT connector for on a keyboardless MIDI sound module
To send out midi data to be play by the sound module.
46 - You are using a MIDI sequencer to record many complex tracks to be played on a MIDI system where several modules are chained together, THRU to IN. What might happen if you use Pitch Bend or Control Change messages excessively?
The Pitch Bend Change message is normally sent from a keyboard instrument in response to changes in position of the pitch bend wheel. The pitch bend information is used to modify the pitch of sounds being played on a given Channel.
These messages involve a lot of data. When combined with a need to drive several modules, this can produce data traffic overload manifesting itself in increased latency problems.
47 - Some MIDI equipment processes data from the IN connector before sending it to the THRU. What effect does this have on timing?
Time delays, and or increased latency.
48 - You are mixing MTC on the same cable as musical data. How might this affect the timing of notes?
Time delays, and or increased latency.
49 - You have connected a keyboard with 32 note polyphony to a sequencer and you find that it is only capable of 16 note polyphony when played manually. If the keyboard can give the full 32 notes when disconnected from the sequencer what has happened?
Sequencer can’t handle 32 note polyphony.
50 - You are recording a melody into a sequencer. The melody contains a complex series of notes and pitch bend movements and you can’t get both the notes and pitch bend moves right simultaneously. What should you do?
Record first the notes, and the pitch bend later.
51 - You have recorded a piano sound into a sequencer performed by a keyboard player who tends to use the sustain pedal a lot. What problem might you find if you record another piano part on the same MIDI channel?
We are going to have a real mess. Notes recorded from the second piano are going to be affected by the sustain recorded in the first piano.
52 - You have sampled a four bar drum loop and you trigger it from the sequencer on the first beat of bar 1. You also trigger it on the first beat of bar 5. What will happen if you play the sequence from bar 3?
If I understood what you mean, you will only hear half of the first loop (3 and 4 bar) and a complete one from bar 5.????
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