Modular synthesizer · 1964
Moog modular synthesizer: how the first commercial synth works
The Moog modular synthesizer, first shown in 1964, was the first commercial synthesizer: separate oscillators, filters, amplifiers and envelope generators joined by patch cords and controlled by voltages. Built to order until 1981, it set the one-volt-per-octave standard modular systems still use.
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Voltage control and one volt per octave
Earlier synthesizers such as the RCA Mark II filled rooms, generated sound with hundreds of vacuum tubes and were programmed with punched cards. The Moog design used newly available silicon transistors whose output current rises exponentially with the input voltage. With them it built the voltage-controlled oscillator (VCO): change the voltage and the pitch changes. Voltage control — using one voltage to set another module's behaviour — was the principal innovation, and it is why a keyboard, a sequencer or another oscillator can all "play" the same module.
The system was designed around a standard of one volt per octave: each extra volt raises the pitch by an octave, and each octave divides evenly into twelve semitones. Loudness was controlled the same way with voltage-controlled amplifiers (VCAs), and the modules use a 0–5 V range for their other parameters. Roland, ARP, Sequential Circuits, Oberheim and today's Eurorack makers all adopted volts per octave.
The first prototype had just two oscillators and an amplifier. Because an oscillator's output is itself a voltage, one could modulate another — producing vibrato and tremolo — which demonstrated the idea immediately.
The modules and what each one does
| Module | What it does | Worth knowing |
|---|---|---|
| Oscillator (VCO) | Produces a raw waveform at a pitch set by voltage | Sawtooth is bright and brassy, triangle thin and flute-like, pulse nasal and reedy, sine whistle-like; small temperature changes make them drift quickly |
| Filter (VCF) | Removes frequencies to shape the tone | The 24 dB low-pass "ladder" filter boosts frequencies around the cutoff; overdriven, it distorts in the way called the Moog sound |
| Amplifier (VCA) | Sets loudness under voltage control | With an envelope, it makes a note start and stop |
| Envelope generator | Sends a voltage that rises and falls each time a note is played | Invented so notes could fade in and out; the prototype used a doorbell button |
| Noise generator, mixers, triggers | Supply noise, combine signals and start events | Nothing sounds until a workable chain of modules is patched |
| Controllers | Keyboard, ribbon, joystick, pedals or a sequencer | The ribbon controller bends pitch like a finger sliding along a violin string |
The ladder filter — named after its transistor pairs and capacitors arranged like the rungs of a ladder — was the only part of the design that was patented, on 28 October 1969. Requests from composers shaped other features that became standard: a touch-sensitive keyboard, portamento and a fixed filter bank. Whether a synthesizer should have a keyboard at all was debated at the time; the company included one because most customers wanted it, and it made the instrument look like something to make music with.
No sound until it is patched
A modular synthesizer has no default sound. A typical first patch runs keyboard pitch to an oscillator, the oscillator to a filter, the filter to an amplifier and the amplifier to the output, with the keyboard's trigger starting two envelopes — one for the filter, one for the amplifier. Every change of sound means moving cords and knobs, and there is no way to save a setting.
Early owners had no manuals or books to learn from; they taught themselves, swapped knowledge by word of mouth or attended seminars run by the company. The same discipline applies today: if a modular sound matters, it has to be documented by hand.
Document a patch in three passes Photograph the whole system; list every cord as "from module and jack → to module and jack"; then note the knob positions of each module the cords touch. With those three records a patch can be rebuilt on another day.
Check the trigger type Early Moog modular systems start notes with an S-trigger, which shorts the line to ground, while most later gear sends a positive V-trigger. Connected without an adapter, the two will either stay silent or play backwards — sounding with no key down and stopping when a key is pressed.
A short history, 1963–today
| Year | What happened |
|---|---|
| 1963 | A meeting at a New York State school music trade fair leads to the idea of a "portable electronic music studio"; a US$16,000 state small-business grant funds work in Trumansburg, New York |
| 1964 | The synthesizer is demonstrated at the University of Toronto's electronic music studio and at the Audio Engineering Society convention in New York in October, where the first orders are taken |
| 1965 | Production of modular systems, built to order, begins |
| 1966 | The word "synthesizer" is used in print for the first time; the company had called its product a system of electronic music modules |
| 1969 | The ladder filter patent is granted on 28 October |
| 1970 | Only 28 systems belong to musicians; the portable Minimoog appears and modular systems become a secondary business |
| 1981 | Production of modular systems ends |
| 1990s | Patents and rights to the modular circuits expire |
| 2014–2015 | Moog Music builds modular systems again |
A complete system cost about US$10,000, far less than the six-figure sums of the room-sized machines before it. For a time the American Federation of Musicians negotiated a ban on its use in commercial work, because session players feared an instrument that could imitate strings and horns would take their jobs. In 1982 the original prototype was donated to the Henry Ford Museum; in 1989 a system sold in 1964 entered the Stearns Collection of Musical Instruments at the University of Michigan.
Formats, clones and software today
Moog-style modules are known as the 5U or "dotcom" format, after the rack height and a maker that built compatible modules once the originals were discontinued. The smaller Eurorack format has since overtaken it as the dominant modular standard, and Moog circuits have been cloned in Eurorack form since 2020. In software, Moog's own Model 15 app emulates one of its modular systems (iOS from 2016, macOS from 2021), and other plug-ins model the whole system.
For a session, a vintage modular raises the same questions as any pre-MIDI instrument — volts per octave, trigger type, warm-up time — plus one more: how much time the patching will take. Smaller self-contained descendants such as the Minimoog and the semi-modular ARP 2600 were built precisely to make that faster.
Frequently asked questions
Was the Moog the first synthesizer?
It was the first commercial synthesizer. Earlier machines such as the RCA Mark II filled rooms, used vacuum tubes and were programmed with punched cards; the Moog modular was smaller, cheaper and could be played in real time from a keyboard.
What does one volt per octave mean?
It is a pitch-control standard: each extra volt of control voltage raises the oscillator's pitch by one octave, so 4 V sounds an octave above 3 V, and each volt divides evenly into twelve semitones.
Are Moog modular synthesizers still made?
Original production ran from 1965 to 1981. Moog Music began building modular systems again in the mid-2010s, and compatible 5U and Eurorack modules are made by other companies.
Keep reading
- Minimoog Model D: the first synthesizer sold in shopsThe Minimoog Model D explained: three oscillators, a 24 dB ladder filter, 44 keys and the first pitch wheel, how it came about, its reissues and studio tips.
- ARP 2600: the semi-modular synth, plus the Solina and Pro SoloistThe ARP 2600 explained: a semi-modular synth with three oscillators, a 24 dB filter and spring reverb, its versions and reissues, the Solina and Pro Soloist.
- Oberheim synthesizers: SEM, Four Voice, Eight Voice and Matrix-12Oberheim synthesizers explained: the SEM and its multimode filter, the Two, Four and Eight Voice that first played chords, the OB series and the Matrix-12.
- Renting vintage synths for a session: what to ask before you bookRenting vintage synths for a session or tour? What to ask about memory, MIDI and CV, mains power, warm-up, weight and cables, from the instruments' specs.
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