DuetMind
A local improvising partner that shows you its plan a beat before it plays it, then answers your phrase — trading fours, developing your motifs.
auto-demo playing both parts
Play the home row A S D F G H J K (a C-major octave) and the row above Q W E R T Y U I (the octave up), or tap the keys. The instant you play, the demo hands you the lead.