DX21

The Yamaha DX21 is a digital synthesizer that produces sound by four-operator FM synthesis with eight algorithms, a simplified engine compared with the six-operator design of the DX7. Released in 1985, it provides eight-voice polyphony, a 61-note keyboard without velocity sensitivity, a built-in chorus effect, MIDI, and a bi-timbral mode in which two voices can be used at once with polyphony divided between them. It is generally used for the bell, electric-piano and bass timbres characteristic of mid-1980s FM instruments.