Moog Opus 3 is an analog synthesizer with 3 fixed-purpose oscillators. It was designed by a well-known specialist in the field of synthesis engineering - Dr. Herbert Deutsch - who initially contributed to the fact that Robert Moog began to create synthesizers. Opus 3 has three sections for sound building - strings, brass and organ. String and brass have their own separate filter sections, the organ does not have one. The filter has the ability to adjust the attack, release and sustain of the envelope generator.

A distinctive feature of this synthesizer is that it has two sound output channels for creating a stereo effect with instruments and chorus effect panning, and a separate section on the front panel with control for adjustment of these positions.

Opus 3 has a 4-octave keyboard, as well as the convenient layout of all controllers, as well as the sound that is inherent in many analog instruments of those years in its price category. Despite some criticism that the sound is too stiff considering the dynamics and the frequency range, it is warm, pleasant and old-school. Kraftwerk used to like it, although it doesn’t belong to Moog's classics, and purists who’re in love with Moog do not actually like this unit. You can’t buy it for sane money (~ 400-600 dollars), and it’s difficult to sell it either.