@borfo: yes and yes. Here’s how it works:
1. MidiREX processes incoming MIDI events on the channel it is set to. All other channels are ignored and passed to MIDI OUT as is.
2. When recording, MidiREX stores events with their original channel (that would be the channel MidiREX is set to).
3. When playing back MidiREX sends track events out overriding their channel with MIDI channel the track is set to unless the track channel is set to OMNI, in which case events are sent out as is with the original channel they where recorded on.
4. When merging tracks, MidiREX essentially plays back both tracks’ events into the target track, so if source tracks have different MIDI channels, resulting track will contain events on different channels as well. During playback, these events’ channels will be overriden with track’s channel unless it’s set to OMNI, in which case single track will play more than one channel.
In fact, it’s very common to bounce related tracks into one to free up a track: for example, you recorded drums, bass, pad and lead lines on tracks 1,2,3,4 then merge drum and bass into track 1 to free track 2 for more arrangement.