Bee Gees Rhythm Machine, produced and marketed by Mattel in 1978 : : 20 keys (A through E) and four buttons. The first three buttons were pressed to synthesize a disco, latin, or pop rhythm, and the fourth controlled the tempo. On the top of the rhythm machine was a tuning knob, capable of adjusting the pitch an octave in either direction, and a volume knob. The rhythm machine required a 9-volt battery and was packaged with a music book.
