From The FAQ (already mentioned )
Q: How do I make my QY70 ignore my MIDI keyboard's channel, and always record on the active track?
This is convenient, because you can leave your keyboard on channel 1 all the time, and just hop to different tracks in the QY70. This feature isundocumented. Do MENU/UTILITIES, MENU/MIDI. The MIDI THRU setting can be OFF, THRU, or RECMONTR. In RECMONTR mode, the QY70 will translate your keyboard's output to whatever track you're working on. It will also apply any MIDI filter you've selected (on the same screen). When would you NOT want RECMONTR? If your MIDI input contains several channels, meant to trigger multiple tracks in the QY70. Be aware thatthe RECMONTR setting also affects what comes out the MIDI Out connector.
That is, turn RECMONTR off and program both the QY (SONG mode is a good idea to have a fixed palette of 16 voices) and the external MIDI keyboard to use as many channels you want, this is a field where having a controller able to do plenty of layers and splits would do.
I had some notes I made years ago to apply this technique by partitioning my PC3K7 keyboard on a setup (i.e. Kurzweilspeak for what all others call a "multi") defining several zones on the keybed to have a bass sound in the lower left, a pad in the mid left octave and from C4 rightwards a rhodes and a lead, on Kurzweils you can switch on and off what happens on the 16 channels, so that each keyboard zone, assigned ti a given MIDI channel, can be turned on or off, thus exploiting the QY as a sound module.
Actually, I prefer the opposite, since in my case I find that the QY (both 100 and 700) are better suited on sequencer duties (the PC3K has a 16 track 960 ppq sequencer but the interface is oh well), and the PC3K is excellent as sound generator. I work as the OP desired when I'm recording on the QYs, anyways.
HTH
prea