Yamaha DX21 Keyboard Synthesizer (LED Upgrade + Branded Gig Bag) (MIJ)Yamaha DX21 Essentially a miniature DX7, 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. It uses sine wave based frequency modulation (FM) synthesis. It has two 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