- Programmable 4-operator 8-algorithm digital FM tone generator
- Independent 5-parameter envelope generator for each operator
- 32-voice internal RAM memory
- 128 voices programmed into internal ROM
- Built-in cassette interface for voice data storage
- Single, Dual, and Split play modes
- 32 performance memories can be programmed with voice combinations and other performance parameters
- Built-in stereo chorus effect (only DX-21)
- 61-key keyboard
- The DX21īs keyboard itself does not have key velocity, but its tone generator accept key velocity data from an external MIDI source
- Sustain footswitch, volume foot controller and breath controller inputs
- MIDI IN/OUT/THRU terminals
