A monophonic synth introduced by Moog Music in 1970. Prior to that time, Moog had produced only modular synthesizer systems -- the ultimate in flexibility and sonic capability in its day, but large, heavy, and difficult to manage when playing live. In 1968, Bob Moog had conceived of the idea of a stage synth, containing the most-often used components from a modular, and simplified routing choices selected via the use of panel switches instead of patch cords. Over the next two years, four models were prototyped, known as the Models A through D.
The Experiments: Models A, B and C
Model A was basically a collection of modules from the modular system, integrated into a case with the keyboard. This was put together for the purpose of deciding which synth circiuts and features the Minimoog should contain, and how signals should be routed internally. It was never intended to be a design prototype.
Models B and C experimented with circuits, packaging and panel layout. A few prototypes were built and loaned out to musicians for feedback; jazz artist Sun Ra used a Model C on an album. But neither of these went into production.
The Definitive Article: Model D
Model D turned out to be the definitive article. The control panel which tilts up from the case, the controls layout, knob style, colors, and the wood sides are all characteristics that are now associated with the Minimoog.
The Model D went into production in late 1970, just before Bob Moog sold the company to an investor. Over time, several engineering changes were introduced; the original VCOs were not very stable, and two other designs were used over the synth's production run. The casing had holes added to provide access to trim pots for calibration; the panel face changed from metal to plastic; the key mechanism changed, and several different combinations of rocket switch covers were used. But the basic concept remained the same: a three-VCO monosynth (one VCO could be switched to an LFO range), feeding a VCF, along with a white noise generator. The VCF fed through a mixer to the VCA, along with an external input. The three-segment envelope generator could be set for attack-sustain-release mode, or an attack-decay-sustain mode with instantaneous release at key up.
The Model D is recognized as being the commercially produced synth to include a pitch wheel and mod wheel, two performance controls which are now seen on most synths. The keyboard was a somewhat peculiar 3-1/2 octave affair with the lowest note being an F, as opposed to most keyboard instruments which have a lowest note of C. The synth was packaged in a wooden case which held the keyboard and the control panel, which had the electronics enclosure and most of the electronics mounted to it. This part was hinged and could be tilted up out of the case to face up at an angle, making it easier for the performer to see the controls without having to lean over the synth. The panel could then be laid flat and latched down for transport. Photographs of the Model D nearly always show it with the panel tilted up.
Starting in the mid-1970s, third party companies began introducing upgrade and enhancement packages for the Minimoog. The most radical of these was the late-1980s Studio Electronics MIDImoog, which took the boards containing all of the sound-generating and processing components out of the Mini's case, installing them in a new rackmount synthesizer case which provided a MIDI interface.
According to the Moog Archives, Minimoog production temporarily stopped in 1975, after the company's sale to Norlin. It resumed in 1977 and continued until 1981. Over 13,000 units were sold; at the time, these were records for length of production run and number of units sold for a synth. Possibly about a third of these remain today in working or repairable condition; the Model D is now a highly sought after collector's item. All of the prototypes are accounted for; the Audities Foundation has the Model A, one of the two Model B units, one of 4 Model C's and the Model D prototype.
After Moog: The Model E and the Midimoog
In 1998, a Welshman named Alex Winter acquired the UK rights to the Moog name and designs. He managed to produce copies of the Minimoog circuitry, and his company put into production a new version of the Minimoog with a few improvements (mainly the addition of MIDI). Although these were the first new Minimoogs to be produced since 1981, the list price discouraged most buyers and the company folded after producing only a handful of units, probably less than 100. These are now referred to by collectors as the "Welsh Minis", or the "Model E", even though Bob Moog had nothing to do with them.
As the original Moog Music was being liquidated in the late 1980s, a California company called Studio Electronics succeeded in obtaining a stock of Minimoog circuit boards from a closeout sale. They designed a rack-mount case to accommodate the boards, with the addition of a MIDI interface and a revised panel to fit within the dimensions of a 19" rack. This became the Midimoog. About 500-700 were built; unfortunately, at some point SE ran out of boards, and some units were built by gutting existing Model D's.
The New Moog Music and the Voyager
In 2002, the reconstituted Moog Music began producing a new model, the Voyager. This bore a resemblence to the original in packaging and panel layout, and used many of the same basic circuit designs, but it also bore many new microprocessor-enabled features. This was one of Bob Moog's last projects before his death in 2005. In the UK they are sold as the "Voyager by Bob Moog", because the aforementioned Alex Winter still owns the Moog Music trademarks in the UK, even though he is no longer producing anything.
The Model D Revived, Briefly
In 2016, Moog put a revived version of the Model D back into production. Moog claims that the circuitry is a faithful copy of the original, although it is not clear what VCO design Moog used, since the VCO in the earlier production of the original Model D was not noted for tuning stability, and the improved VCO used in the later production relied on the uA726 thermally controlled transistor pair, which is long out of production. Improvements in the new Model D include a dedicated low frequency oscillator (in addition to the three VCOs), a second envelope generator for modulating the VCF, a very basic MIDI interface, and a Fatar keyboard mechanism that is velocity and aftertouch sensitive. The velocity and aftertouch are not routeable internally, but are taken out to jacks at the top/back edge of the panel where they can be routed to a few internal destinations using patch cords. A CV/Gate interface, the addition of which was a common modification on the original, was included. This remained in production for about a year.
Behringer Clones the D
In 2017, Behringer began offering a clone of the Model D, with features very similar to Moog's Model D revival, but at a far lower price (which was and is somewhat controversial). A significant difference is that the Behringer D is formatted and sized to be Eurorack compatible; it can be removed from its case and mounted in a Eurorack-format modular synth, with patching jacks across the top edge of the panel.