Dan,

Please be sure to map all the functions to MIDI (sys ex) commands and provide return status, so that commercially available MIDI controllers can be used to control various functions as mapped. The status signals can be used to drive the indicator lights associated with each button.

This will go a long way in making this a user-friendly performance system, rather than point and click studio only system.

Also, as other have indicated before, playing existing styles (even from only one manufacturer) is a big plus.

Good luck,

Alex