bernie,
my memory may be a bit hazy on this, but i seem to recall you can assign an expression pedal to control only the sequencer (which is what is playing the files),which then leaves the master control for your other playing, and/or you can assign that same function to one or more of the onboard sliders...if you have a PDF manual for the pa, just do a search function within adobe reader for the word assign, or similar it will be there somewhere (in know it could be done on the pa1x, because i did it all the time when using my midis, i used a foot expression controller so i could adjust the live keyboard playing against the midi file)...i would ask the question again on the korg forum at irish acts...
cheers
dennis