A monophonic analog synth produced by Moog Music starting in 1981. It is a fairly basic synth aimed at a low-end price point, with a conventional subtractive voice architecture having two voltage controlled oscillators, one voltage controlled filter, one voltage controlled amplifier, one envelope generator, and one low frequency oscillator. However, it also contains some additional atypical features, which relate to the unique way that the MG-1 was intended to be marketed.
The MG-1 was sold, as a home entertainment instrument, by the Radio Shack electronics store chain, under its Realistic brand name (which Radio Shack typically used to market home audio and amateur radio equipment). A small legend next to the logo noted "by Moog". The idea was hatched by Moog's Dave Luce, who attended a Radio Shack conference with a monophonic synth cobbed together from Minimoog circuit boards. Radio Shack was intrigued by the basic idea, but thought that it needed work to be marketable to the home audience, and to hit a price point that would fit into Radio Shack's marketing. Radio Shack turned the idea over to Paul Schreiber, who at the time was an employee of Tandy Corporation, Radio Shack's parent company. Schreiber laid out the voice architecture with the two VCOs, a standard Moog transistor ladder VCF, and the other voice components. He added to this a ring modulator and a noise source. The VCO design was surprisingly versatile for a low-cost synth, with triangle, sawtooth, and pulse wave selection for each VCO, detuning, and oscillator sync. The envelope generator had several sustain modes, and could be retriggered by the LFO. A Moog keyboard with a 2-1/2 octave, F-to-C span (a standard design for Moog products of the time) was fitted. Omitted were pitch and mod wheels, for cost reasons. Schreiber also had to specify some other components of a lower specification than those typically used by Moog, in order to hit the price goal, and in order to have some "look and feel" commonality with other products sold under the Realistic name.
The most unusual feature was the "polyphonic" section, added at the insistence of a Radio Shack executive. This was a basic divide-down organ circuit which generated only square waves. It was fully polyphonic; all 32 keys could be held down and all 32 would sound. It had no modulation options, although it could be detuned. It was mixed with the outputs of the VCOs at the VCF input. Due to circuit limitations, any given key could generate the polyphonic sound only as long as the key was held down; when a key was released, that key's polyphonic waveform cut off immediately, regardless of the envelope generator settings.
The colorful panel, atypical for a Moog product, was designed to be "friendly" to the home user not familiar with synthesizer terminology; e.g. "tone source" instead of "voltage controlled oscillator". The colors served as signal routing cues. In keeping with its intention to be used in a home audio system, the audio input and output jacks on the rear panel were RCA jacks (the standard for home audio equipment at the time), rather than phone jacks. The audio inputs were simply mixed with the synth's output, the idea being that the user could play music in through the audio jacks, play along with the music, and hear the mix of the two at the outputs. (This is why the synth has left and right output jacks, despite the fact that its own signal is strictly monaural.) The front edge of the case included a headphone jack. Interestingly, the MG-1 did have a CV/Gate interface (the gate being Moog's S-trigger, despite using a 1/4" phone jack), which likely was not used by many of the intended customer base.
In the history of synths designed and marketed to the home entertainment market, the MG-1 came closer to success than any other product of the era. No good sales estimates are known, but it appears that Radio Shack sold several thousand of them. Although it didn't appear in the catalog until 1982, the MG-1 first appeared in stores in 1981, and remained available through about 1984.
The cross-licensing agreements between Moog and Tandy allowed Moog to begin marketing its own "pro" version 18 months after the introduction of the MG-1. Moog made some changes to the design and this became the Moog Rogue, first appearing in 1982. It used the same case and keyboard, but the panel was revised to include pitch and mod wheels, and the polyphonic section was removed. Unfortunately, the additional panel space required for the wheels meant that some other controls had to be removed; the separate controls for the two VCOs were eliminated along with some routing options, and some sliders were replaced by on-off swtiches. It is unclear how many Rogues were built, or how long it remained on the market.
Today, the MG-1 is considered a hidden gem by collectors looking for the classic Moog sound at a reasonable price. A large number of them were likely little used by their original owners, and so ones in good condition remain in the market. An issue is that a high-density foam used to fill space under the panel has deteriorated into a tar-like substance over time, and is time-consuming to clean up. Other than that, the synth components have mostly held up well. A large variety of mods have been published, ranging from pulse width modulation for the VCOs, to MIDI interfaces.