In a chord progression input/modification device, when a key and a single or two successive reference chords are designated by a user, available chords are acquired and displayed. Any one of the available chords can be used, in consonance with musical theory, to follow or substitute for the single...http://www.google.com.hk/patents/US5852252?utm_source=gb-gplus-share專利 US5852252 - Chord progression input/modification device
