For use in or with an electronic musical instrument, an automatic accompaniment apparatus has a keyboard, a chord detector detecting a chord played on the keyboard, a judging circuit judging chord establishment of the detector chord, and a chord accompaniment tone generator producing, in accordance with...http://www.google.co.uk/patents/US4887504?utm_source=gb-gplus-sharePatent US4887504 - Automatic accompaniment apparatus realizing automatic accompaniment and manual performance selectable automatically
