Dave Smith Instruments SYNTHESIZERS

Hi

I have a PEK, and I'm trying to figure out if there's a way to vary a 
programmed sequence from major to minor, to work in a certain key. 
Almost like, in a Casio, you could get a minor chord by playing a minor 
third with the root in "auto-accompany" mode.
In other words, say, in the key or C, when I hold down a C, it plays a 
major chord or sequence, then when I hold down an A, it plays  minor. 
Could a footswitch modulate pitch (just the third)? Is there a way to do 
it as a split in Combo mode? I'm trying to wrap my brain around the 
easiest way to do it in a live performance.

thanks,

Joe McGinty