Comment by rzzzt

The Windows 3.1-era Band-in-a-box had a feature (and probably still has, if that software is still around) that allowed playing along a pre-programmed chord progression in different styles, which always produced a harmony that matched the current chord with a a single key press. You could play in the style of eg. Erroll Garner, even if you only knew how the "bare" melody of the song goes.