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"The Moog Opus 3 is a vintage polyphonic synth that combines string, organ and brass sounds in a four-octave keyboard, along with flexible controls for shaping each sound.
One of the coolest things about the Opus 3 is that it has a classic Moog four-pole filter that the brass and organ can be run through. The filter has the sound Moogs are famous four, and it can be run into self-oscillation.
The synth also features a three-phase chorus effect that uses the famed Reticon bucket brigade chips, as well as stereo and mono outputs.
Here are details about the unit for sale:
The old, deteriorating foam that sat below the control panel has been removed from this one, so you don’t have to worry about it.
All of the sliders, switches and rotary controls — except for the master volume — were changed out for New Old Stock replacements. All the slider caps and control knobs are New Old Stock as well. Everything works smoothly, with no noise or issues.
The master volume has very minor crackle at the top end of its range while it’s being moved. It is otherwise noise-free during normal operation. I would have had it changed out but it wasn’t possible to source an original replacement.
One of the three original Reticon chips in the chorus effect was replaced when an original failed. All three are working, and the chorus sounds great.
The original red LED in the Modulation section was swapped out for a new bright blue LED.
I wasn’t able to test the sustain jack on the unit’s front panel. Moog chose an unusual size jack here— it’s slightly smaller than a 1/4-inch input. It would be easy to swap it out with a proper 1/4-inch jack if you choose to do so.
The physical condition is very good. Note the scratches to the wood and some minor marks on the faceplate.
All of the notes sound as they should, and all controls and functions work as they should.
HELPFUL NOTES
Although its functions are basic, you’ll need to understand the signal routing in the Opus 3. These are spelled out in the owner's manual (which is available online), but knowing the following will help you get your head around it.
For example, the chorus effect operates on the strings and organ, not on the brass. This is by design and is noted by an arrow on the control panel.
The Moog four-pole VCF can be used on the organ and brass, not the strings. Again, this is by design and is noted by an arrow on the control panel.
Frequency Modulation works on all sounds, but VCF modulation only works on the organ and brass because these are the two sounds that can be run through the VCF (see the point immediately above). Again, this is by design.
The length of chorus delay is set by using the delay fader in the Modulation section. This too is by design.
Two other noteworthy points:
• The pitch wheel has a firm detent (the point at which it sits at pitch). Other owners have noted the same thing about their units in online forums. It’s not difficult to work, but it’s firmer than on other synths I’ve owned.
• All of the electronics, aside from those mentioned above, are original and working fine. Electrical components can fail or become damaged with time and/or misuse. Always be sure you are connected to proper voltage, and note that ground loops can introduce hum."
It includes both manual and voltage control over FM Index, Ratio and a selection of classic operator waveforms for a wide palette of FM sounds from a simple set of controls. A built-in decay envelope is routed to both FM depth and output level, allowing the FMco to function as a full synth voice when triggered. The FMco also includes CV-controlled four-voice chords, an encoder-based tuning system for easy accurate pitch control, and a stereo-widened output, delivering a large amount of FM synthesis all in just 8HP.
