It strikes me that it would not be that hard to code an app for the iPad (or a Windows tablet, whatever) to add a Chord Sequencer to any arranger out there.

Basically, all it has to do is slave to the arranger's tempo clock (easy), receive the NTA (notes to arranger) channel from the arranger, and loop the MIDI recording and play it back when the Play button is hit. Hardly as complicated as a full sequencer...

I'm pretty sure this would sell very well. Anyone know anyone doing MIDI app development for iPad or other devices?