Basically I want a basic interface (ideally on my PC rather than on a phone) where I can lay out a chord sequence, have it loop with a basic accompaniment, then maybe modulate it (e.g. ii-V-I starting in C then moving through the circle of fifths). I just want to play over some basic chords without getting bogged down trying to play or program it in Reaper.   Hopefully someone's already done this so I don't have to go build it myself...