PianoMaestro Learning System - Fits Casio PX-5S PX-780 PX-850BK PX-750WE PX-750BK PX-150WE As seen on TV, WIRED and Gizmag! Learn to play any piano piece in 30 days, or your money back Adds guide lights to ANY acoustic or digital piano  reads standard piano MIDI files Works with PC and Mac (Mac via download) Slow down playback, practice left and right hands separately, repeat a few notes at a time