Zoë Blade's notebook

900 Series (Moog)

900 Series tech specs

Various modular synthesisers were made by Moog in the 1960s and 1970s, known as the 900 Series, 900 System, or simply Moog Modular, although there doesn't appear to be a definitive name for the range as a whole... or any one system in the range.

Moog's modular system grew out of various good ideas that Moog's clients had asked him to implement. In 1964, he prototyped a modular system with voltage control for Herb Deutsch. This was inspired by Harald Bode's modular system, although Moog added a musical keyboard and introduced the 1 volt per octave standard for relaying pitch information from the keyboard to the oscillators. Moog built VCAs, ADSR envelope generators, and envelope followers to Vladimir Ussachevsky's spec in 1965,[1] which presumably became the 902, 911, and 912 modules respectively. Also in 1965, for Gustav Ciamaga, Moog designed a voltage controlled filter.[2] This likely became the smooth, creamy sounding 904A which, along with an excess of detunable oscillators, gave his synthesiser its signature sound.

The whole range sounds great — and big — but if you're used to more recent modular synthesisers such as Roland's System-100M or Doepfer's A-100, bear in mind that equivalent patches on a Moog 900 Series might be significantly more longwinded. These systems were trailblazing, and so lack many modern conventions, from features through to terminology.

For example, the CV inputs of modules like the oscillators, amplifier, and filters don't have built-in attenuators to specify how much each control signal affects them. So you'll likely be using additional attenuator, amplifier, or mixer modules on the way into those.

A more sensible approach when dealing with modern clones might be to simply get that smooth, creamy filter, and combine it with modules from another system that has more modern conveniences. But then again, there is that aesthetic...


My favourite instrument is my old Moog III system, and I use its twelve envelope generators together to create specific sound shapes. It's also useful for treating the computer processed sounds, and even though working with this analogue system takes longer to set up (tuning, patching etc), it gives me plenty of freedom because I can choose all the connections independently — and that's impossible for my digital systems.

— Isao Tomita, 1983[3]

...a big Moog was ideal and it sounded good. It still sounds better than anything else around. I have a theory that every year the manufacturers make synthesizers that sound slightly less good but have more functions. But it's really quite peculiar that if you set up one sound on any of the synthesizers around at the moment and you set up the same sound on the Moog — particularly bass sounds — the Moog just has so much more punch and quality. And that's why it's still around.

— Hans Zimmer, 1986[4]

I built some equipment for Ussachevsky in 1965. I built two voltage controlled amplifiers, two envelope generators, and two envelope followers. Ussachevsky wrote the specifications for these modules. He wanted the envelope generators to have four parts: attack, decay, sustain, and release. He was the first one to specify the ADSR envelope. Now it is standard on electronic synthesizers and keyboards.

— Bob Moog, 2000[1]

Standard configurations

The first series of complete systems were the Synthesizer I, Synthesizer II, and Synthesizer III from the 1960s.[5] These evolved into the Synthesizer Ic, Synthesizer IIc, and Synthesizer IIIc "console" (studio) versions, so named to differentiate them from the Synthesizer Ip, Synthesizer IIp, and Synthesizer IIIp,[6] their new "portable" equivalents that replaced the rather fetching walnut cases with black cases with handles.

Synthesizer Ic
901A 901B 901B 991 901 903A 905 907 904A 902 902 911 911 994  
CP3 CP3     CP4 CP8
950 / 956
Synthesizer IIc
960 961 903A 907 984
901A 901B 901B 901B 901A 901B 901B 901 905 904B 904C 904A 902 902 911 911
950 / 956
Synthesizer IIIc
914 905 992 904B 904C 904A 902 902 902 993 911 911A 911 911 912
901A 901B 901B 901B 901A 901B 901B 901B 901A 901B 901B 901B 901 903A 984
950 / 956

These were joined in the early 1970s by the portable Synthesizer 10 and Synthesizer 12,[7] and the Sequencer Complement A and Sequencer Complement B.[6] The complements were based around the new 960 Sequential Controller module, an analogue step sequencer, and both the A and B complements were available in studio or portable cases.

This time, the 960 wasn't based on something Moog had built for a friend, even though he had previously transistorised one of Raymond Scott's sequencers. Instead, it was based on rival Buchla's Sequential Voltage Source Model 123.

Sequencer Complement B
960 962 994 961 960 962

Finally, after a change of company ownership, the range was cut back to a more manageable three offerings: the portable Synthesizer 15, and the studio-bound Synthesizer 35 and Synthesizer 55, all of which replaced the 901 oscillators with more stable 921 equivalents.[8] The Synthesizer 55 is rather opulent, offering an iconic three rows of modules towering above its keyboard.

As this is all clearly too simple, yet more variations of these product names exist, replacing the "Synthesizer" with "Model", and eventually "System".

System 35
921A 921B 921B 923 921A 921B 921B 921 907 904B 904A 902 902 902 911 911 911
CP3A CP3A CP35   CP4 CP8
System 55
914 904B 904A 992 902 902 911 911   902 902 902 993 911 911A 911 911
921A 921B 921B 921B 921A 921B 921B 921B 921 995 903A 994 960 962


Model Type Released Description
901 Module 1965[9] VCO (Doubles as LFO)
901A Module 1965[9] Oscillator controller
901B Module 1965[9] Oscillator
901C Module 1965[9] Output stage
901D Module 1965[9] Variable waveform output stages
902 Module 1965[9] VCA
902A Module 1965[9] Bandpass filter adapter
903 Module 1965[9] White noise
904 Module 1965[9] Multimode VCF
904A Module 1965[9] Lowpass VCF
904B Module 1965[9] Highpass VCF
904C Module 1965[9] Bandpass and notch VCF
905 Module 1965[9] Spring reverb
906 Module 1965[9] Impulse generator
907 Module 1965[9] Fixed filter bank (8 bandpass, 1 low, 1 high)
910 Module 1965[9] Power supply
911 Module 1965[9] ADSR envelope generator
912 Module 1965[9] Envelope follower
913 Module 1965[9] Triggered envelope generator
920 Module 1965[9] Power supply
950 Controller 1965[9] Keyboard controller
955 Controller 1965[9] Ribbon controller
982 Module 1965[9] Two-channel mixer
984 Module 1965[9] Four-channel mixer
RM-1 Rack 1967[5] 8-module rack
911A Module 1969[10] Dual trigger delay
950B Peripheral 1969[10] Scale programmer
956 Controller 1969[10] Ribbon controller
960 Module 1969[10] Sequential controller
961 Module 1969[10] Interface
962 Module 1969[10] Sequential switch
N/A Rack 1969[11] 22-module upper walnut rack
N/A Rack 1969[11] 12-module upper walnut rack
N/A Rack 1969[11] 12-module lower walnut rack
903A Module 1971[6] White and pink noise
951 Controller 1971[6] Keyboard controller
958 Controller 1971[6] Foot pedal
959 Controller 1971[6] Joystick
991 Module 1971[6] Highpass and lowpass filters / attenuator
992 Module 1971[6] Control voltages / attenuator
993 Module 1971[6] Trigger / envelope voltages
994 Module 1971[6] Multiples
CP1 Module 1971[6] CV and trigger out
CP2 Module 1971[6] Lowpass and highpass filters / multiples / CV and trigger out
CP3 Module 1971[6] Mixer / trunk lines / CV switches / attenuator
CP4 Module 1971[6] CV switches / attenuator / trigger and envelope routing switches / CV and trigger out
CP5 Module 1971[6] CV and trigger out / power switch
CP6 Module 1971[6] CV switches / attenuator / trigger and envelope routing switches / multiples
CP7 Module 1971[6] Trigger and envelope routing switches / multiples
CP8 Module 1971[6] Power switch
CP9 Module 1971[6] Power switch
CP11 Module 1971[6] Mixer / multiples / attenuator / CV and trigger out / trunk lines / power switch
914 Module 1972[12] Extended range fixed filter bank (12 bandpass, 1 low, 1 high)
921 Module 1972[12] VCO (Doubles as LFO)
921A Module 1972[12] Oscillator controller
921B Module 1972[12] Oscillator
952 Controller 1972[12] Duophonic keyboard controller
1630 Module 1972[13] Frequency shifter (Harald Bode)
1631 Module 1972[13] Ring mod (Harald Bode)
1632 Module 1972[13] Dual ring mod (Harald Bode)
1120 Controller 1973[14] Foot pedal
1121 Controller 1973[14] Footswitch
1125 Peripheral 1973[14] Sample & hold
1130 Controller 1973[14] Percussion controller
1150 Controller 1973[14] Ribbon controller
923 Module 1974[15] Highpass and lowpass filters / White and pink noise
995 Module 1974[16] Attenuators


The 902 Voltage Controlled Amplifier could do with a tad more labelling. Its top input is positive, while its bottom input is negative; and its top output is negative, while its bottom output is positive. Useful, but not obvious.[17]

Notable users

System 55


  1. "An Interview With Bob Moog" 2000
  2. "Abominatron Tape Transfer, Part 2" Seva Ball, Mar 2010
  3. "Isao Tomita" Mike Beecher, Electronics & Music Maker, Feb 1983, pp. 50—52
  4. "No Presets Allowed" Ralph Denyer, Sound On Sound, Aug 1986, pp. 50—55
  5. "Electronic Music Composition-Performance Equipment Short Form Catalog — 1967" Moog, 1967
  6. "Moog 1971" Moog, 1971
  7. "Moog Synthesizer 12" Moog, 1973
  8. "Professional Synthesizers Catalogue '76" Moog, 1976
  9. "Ultra-Short Form Catalog of Electronic Music Composition Instruments" Moog, 1965
  10. "Prices of Synthesizers and Single-Function Instruments Currently Being Produced by R. A. Moog" Moog, 1969
  11. "R. A. Moog Supplementary Price List" Moog, 1969
  12. "Moog Component Price List" Moog, 1972
  13. "Moog System Price List" Moog, 1972
  14. "Moog Inc. Price List" Moog, 1973
  15. "Moog Synthesizer 15" Moog, 1974
  16. "Moog Synthesizer 55" Moog, 1974
  17. "902 VCA Lin v. Exp?" CZ Rider, Mar 2013
  18. "Yards Ahead" Matthew Vosburgh, Music Technology, Nov 1986, pp. 52—55


Deep dives


Modular synthesisers: 100 Series (Behringer) | 900 Series (Behringer) | 900 Series (Moog) | A-100 | Concussor | System-100M

Moog: 900 Series (Moog) | Sequencer Complement