The Casio Casiotone MT-40 is an electronic keyboard, formerly produced by Casio and originally developed for the consumer market. It has 37 main keys and 15 smaller bass keys, with 9-voice polyphony: eight notes may be played on the main keys, and one note on the bass. The bass section has one timbre, and the main section has 22, assignable to one of four presets. Like most small Casio keyboards, it also has a drum section with 6 different beats, a tempo knob, and a "fill" button. The fill button plays sixteenth note pulses of either the "snare" or "kick" as long as it is held down. Production started in the early 1980s and ceased shortly thereafter. The successor of the MT-40 came with a gray case, and was sold as the MT-41.