I don't think I've ever done much with MIDI but there was a short while when I enjoyed playing with Cakewalk. Last try not too many years back was with the Roland GR-55. It was a bit mixed, part my own "playing" (and within my own limitations am rather more comfortable with GDAE 4 string things for melody - mostly folk dance tunes) although I'm not sure that explains why say piano would repeat notes on me and another voice not but quite fun. I'd probably try any module in conjunction with that for one play...