Having a different instrument for each note on a staff (which by default in NWC is equivalent to a MIDI channel) is unique to MIDI channel 10, which is reserved for percussion instruments.  All the other 15 MIDI channels can play only a single instrument (patch) at a time, and the notes on that staff are different pitches over the range of that instrument.  You can change what instrument a MIDI channel plays over the course of a piece, but you cannot have more than one instrument simultaneously on any MIDI channel.

  Hi.

  Milton said "Having a different instrument for each note on a staff (which by default in NWC is equivalent to a MIDI channel) is unique to MIDI channel 10, which is reserved for percussion instruments.  All the other 15 MIDI channels can play only a single instrument (patch) at a time, ....  You can change what instrument a MIDI channel plays over the course of a piece, but you cannot have more than one instrument simultaneously on any MIDI channel."
 
  That's not entirely true.  While it may not be terribly useful, it is possible to start one note by one instrument playing, and then while it's still playing start a second note by a second instrument, ... and so on.

  For example:  in a staff enter a crotchet rest/semibrieve "chord" using the default instrument for the staff, and then enter a crotchet rest/dotted minim "chord" immediately preceded by a MultiPoint Controller instrument change patch ... and then enter a crotchet rest/minim "chord" also immediately preceded by an MPC instrument change patch - and you'll get three different instruments on the same staff playing at the same time (clearly evident if you choose three differently-pitched notes)!

  I did once use this technique on a tied note extending across a barline:  the second bar contained notes for a second instrument; the tied note carried on sounding like the preceding bar's instrument.

  As I said, not terribly useful, but interesting.

  Regards,
  MusicJohn, 7/Apr/06

Neat trick!  I'll have to try it.  My suspicion is , though, that if you took this to a ridiculous extreme and tried to make a single staff play 15 or more different instruments simultaneously that your synth would steal them from channels already assigned to other parts.  Unlike older synths, all newer MIDI synths run in a mode that automatically distributes the instruments playing at any one time to available channels.  If your piece has, say, 10 instruments playing at once and you put another 6 or more instruments on another staff with the technique you described, the synth would turn some of the other parts off or change their instrument to one of the instruments in your multi-instrument staff as it assigned channels to the new notes.  I think it's similar to what happens when you exceed the polyphony limit of your synth.  If your synth can play 32 notes at once and your score temporarily exceeds that limit, some of the notes get cut off in favor of the new notes.