In The discs used by the Optigan are made out of the same material as photo negatives. Instead of grooves, the Optigan discs have little waveforms which are read by a light bar reader inside the Optigan. The discs sits on a felt pad and a brass wheel drops on top of the disc when the drawer is closed. The wheel spins the disc when the Optigan is turned on.
Volume is controlled with a foot pedal.
The unique feature of the Optigan is that the chord buttons do not play a chord when pressed, but an entire band jamming in the key chosen in the style of music that the disc is for. So, pressing the A minor chord button on the Nashville Country disc brings to life a whole country band doing a looped riff in A minor. The five switches above the chord buttons are usually percussion, but sometimes have special effects like crowds cheering or monkeys howling.