The GX-1 has four synthesizer "ranks" or three manuals, called Solo, Upper, and Lower, plus Pedal, and an analog rhythm machine.

The Upper rank also has horizontal aftertouch which can be assigned to pitch, volume or filter, and a polyphonic glide function.

All four ranks use a common voice-card design (called a tone generator in Yamaha parlance) to produce their sounds.

Due to the extensive use of epoxy-potted sub-modules, a complete set of GX-1 voice cards alone weighs more than a Polymoog.

The Upper, Lower and Pedal ranks all have a dual-voice structure, where a different tone is assigned to each of the two voice cards per note.

A set of hidden "wave motion" controls allows the second tones of the Upper and Lower ranks to be de-tuned.