Basically you want the CS to do 4 things at the same time: (1) sync to the drum machine's midi clock, (2) play pre-recorded tracks on external gear, (3) record just a bass line, and (4) play the bass line on an external sampler. Is that it?
To me the simplest thing would be to use a midi router to only send the midi clock to the CS (plus an external keyboard, if you are using that to play parts as well as the CS's pads.
It seems to me that there is no reason to route the channel 15 data into the CS. If its coming from the drum machine, can that be set to only send out midi clock? If not, a router could filter it.
Also, did you check out the MIDI ENABLE parameter? See message 23662, which states:
Possibly an easier option:
In MIDI ENABLE, turn all channels (01B to 16B) to off
"MIDI Enable lets you turn each MIDI channel on and off independently
when in Multi mode. This feature is helpful when you have other devices
connected to the same MIDI line and do not want the XL-7 unit to respond
to the MIDI channels reserved for the other devices."
I think the MIDI IN Block Diagram really helps here.
When the MIDI ENABLE setting is off, the midi in is disconnected from the synth engine--which is what you want, if I understand you correctly.
Hope this helps.
Steve
I am not sure, but that might help. I don't remember if it just disconnects the synth engine from incoming midi data, or the sequencer as well.
Steve