The Opus-3 is one great little synth. It was designed by Herbert A. Deutsch from Hofstra University who originally nudged Dr. Robert Moog into building synthesizers and later served as director of sales & marketing for Moog Music. Herb also wrote the owner's manual. The sounds are broken up into 3 categories: Strings, Brass and Organ. Strings and Brass have their own separate VCF (filter) sections, the Organ section has none. The Opus-3 also has 2 sound outputs for an early stereo effect with panning! It's a colorful little synth with clearly laid out sliders and is fairly straight forward. It has classic analog Moog sound quality and is a great source of some string and lower octave techno-organ sounds. It is used by Stereolab, Kraftwerk, Zonetech, 808 State and The Rentals.