Yamaha DX21

The Yamaha DX21 is a digital controlled bi-timbral programmable digital FM synthesizer with a four operator synth voice generator which was released in 1985 by Yamaha. It uses sine wave-based frequency modulation (FM) synthesis. It has four FM tone generators and a 32-voice random-access memory (RAM), 32 user voices and 128 read-only memory (ROM) factory preset sounds. As a programmable synth, it enables users to create their own unique synthesized tones and sound effects by using the algorithms and oscillators. The instrument weighs 8 kg (17.6 lbs). On its release, it sold for $795.