What is the use of assigning MIDI channel "0" to a track? How do you record many channels to one track at the same time?
Assigning the track is for playback (as far as I understand).
You can record many MIDI channels to a single track by simply recording the MIDI input to that (MIDI) track.
The complication arises during playback when assigning a given patch to a MIDI channel.
By assigning an existing MIDI track to "0" you are not 'forcing' it to be transmitted on a given MIDI channel.
The only reason to assign a MIDI track to a MIDI channel is to force it to send the MIDI data on a different (remapped) MIDI channel.
Use zero if you don't want it to force the MIDI out data to a given channel but rather use the raw MIDI data.
Thanks a lot rharv, it's much clearer now.
Rharv is correct - assigning a MIDI channel only affects playback.