A Beginner's Guide To MIDI 6

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Never Mind The Quality, Count The Notes.
As the use of M.I.D.I. has developed so have the demands placed on the sound modules and synthesisers themselves. As described earlier, in order to construct complete arangements using a M.I.D.I. sequencer you'd need to provide enough sound sources for the sequencer to play. When M.I.D.I. was first introduced this would mean having a separate instrument for each sound that you wanted. However things have thankfully moved on since then.
Today's synthesisers and modules effectively consist of a number of individual sound sources within one box, each of which is capable of playing a different sound source on a different M.I.D.I. channels. These devices are known as Multi-Timbral, literally capable of playing many tones. Devices will vary in the number of different tones that they can play at once, having different numbers of Multi-Timbral Parts. My Ensoniq ESQ1 synthesiser, which is rather dated in terms of facilities, is 8-Part Multi-Timbral. These days it is most common for devices to be provided with 16-part multi-timbrailty. There is a logic behind this number, since if a module has one M.I.D.I In socket then the maximum number of individual M.I.D.I. channels that can be addressed is 16. Further multi-timbrality would therefore be wasted.

Devices also vary in the number of notes or voices that can be played at once. Note that is different from multi-timbrality. Just consider this scenario. An 8-part multi-timbral device has a piano sound assigned to part 1, on M.I.D.I. channel 3 (it is often possible to assign part numbers and M.I.D.I channels independently), and a string sound to part 2 on M.I.D.I. channel 5. You record an 8 note piano chord which is transmitted by the sequencer to the module on M.I.D.I. channel 3. You then record a string melody which is transmitted to the module on M.I.D.I. channel 5, but the device actually only has 8 voices. Two things may happen, depending on how the device assigns voices. Either the strings will not sound, or they will steal notes from the piano part.
The number of notes that are available overall is given by the unit's Polyphony. My ESQ1 is not only 8-part multi-timbral, it is also 8-note Polyphonic. Current devices are generally at least 16-note polyphonic, though 28 and 32 notes are very common, and 64-note polyphonic devices such as the Alesis QS6 are increasingly available. Early multi-timbral devices, like the Yamaha FB01 required the user to specify the number of notes that each part was to have available, but today's units tend to assign voices dynamically, changing the number of voices used depending on what is being played at any one time.