DX21 is actually a cheaper version of the DX7: it has less polyphony and fewer operators , no velocity sensitivity at all, from effects it has only chorus, and it doesnt even have a reverberator. But some of these flaws might actually be its advantages. For example, the Yamaha DX21 owes its unique charm to the 14 bit DA converters that give it a harsh, vintage character, while the imperfect output path give the timbre its characteristic lo-fi hiss. The bass sounds great, and the sound effects are insane.
Download: Yamaha DX21 Solid Bass Preset