‘ARP’ Synthesisers. Alan Robert Pearlman, USA, 1970

Front panel of the ARP 2500
Front main panel of the ARP 2500

ARP Synthesisers was started by the engineer and musical enthusiast Alan Robert Pearlman – hence ‘ARP’ – in 1970 in Lexington, Massachusetts, USA. Previous to ARP, Pearlman had worked as an engineer at NASA and ran his own company Nexus Research laboratory Inc., a manufacturer of op-amps (precision circuits used in amplifiers and test equipment) which he sold in 1967 to fund the launch of the ARP company in 1969. The inspiration for ARP came after he played with both Moog and Buchla synthesisers and being unimpressed by the tuning instability of the oscillators and lack of commercial focus – especially the keyboard-less Buchla Box – and became determined to produce a stable, friendly, commercial electronic instrument.

“If you would like to spend your time creatively, actively producing new music and sound, rather than fighting your way through a nest of cords, a maze of distracting apparatus, you’ll find the ARP uniquely efficient . . . matrix switch interconnection for patching without patch cords…P.S. The oscillators stay in tune.”
ARP Advert 1970

Slider matrix of the 2500
Slider matrix of the 2500

The first product was the ARP 2500, a large monophonic modular voltage-controlled synthesiser designed along similar lines to the Moog Modular series 100. The 2500 had a main cabinet holding up to 12 modules and two wing-extension adding another six modules each. The interface was designed to be as clear as possible to non-synthesists with a logically laid out front panel and, unlike the Buchla and Moog Modular, dispensed with patch cables in favour of a series of  10X10 slider matrices, leaving the front panel clear of cable clutter. The 2500 also came with a 10-step analogue sequencer far in advance of any other modular system of the day

Despite the fact that the 2500 proved to be an advanced, reliable and user-friendly machine with much more stable and superior oscillators to the Moog, it was not commercially successful, selling only approximately 100 units.

ARP 2500 Modules
ARP 2500 Modules

Modules of the ARP 2500

Module # Type of Module Description
1002 power supply
1003 dual envelope generator This module contains two ADSR envelope generators (actually labeled “Attack”, “Initial Decay”, “Sustain”, and “Final Decay”), each switchable between single or multiple triggering. There is a manual gate button as well as a front panel input for gate/trigger and a back panel input for a sustain pedal.
1003a dual envelope generator (same as 1003, except re-positioned trigger switches and gate buttons)
1004 VCO A Voltage Controlled Oscillator with a range from 0.03Hz to 16kHz, this module can function as a VCO or an LFO. It features separate outputs for each of its five waveforms (sine, triangle, square, sawtooth, and pulse) and 6 CV (control voltage) inputs, as well as a CV input for Pulse Width Modulation.
1004p VCO This module is the same as the 1004, except each waveform has its own attenuation knob for mixing all the waveforms together. There is a separate output to for the mixed waveforms.
1004r VCO This module is the same as the 1004, except each waveform has its own rocker switch to route any or all of the waveforms to an extra mix output.
1004t VCO This module is the same as the 1004r, except it uses toggle switches.
1005 VCA andRing Modulator This module is half Voltage Controlled Amplifier and half Balanced (Ring) Modulator. It is switchable between linear or exponential voltage control, and features 11 inputs, 3 outputs, and illuminated push-buttons.
1006 VCF and VCA The Voltage Controlled Filter (24dB/octave, low-pass, with resonance) and Voltage Controlled Amplifier (switchable between linear and exponential) in one module
1012 Convenience Module This module routes two jack inputs to any of the upper ten lines of the lower matrix. (Remember, most of the patching for this instrument is done from these matrix sliders).
1016 dual noise generators This module features two random voltage generators outputting white or pink noise and two slow sample-and-hold circuits, four outputs in all.
1023 dual VCO Both oscillators feature the same waveforms as 1004 with a switch for high and low frequency ranges. There are a total of 10 control inputs and 2 audio outputs.
1026 Preset Voltage module This module contains eight manually or sequencer-driven gated control-voltages, each with two knobs sending control voltages to separate outputs. It can be connected, via the rear panel, to module 1027 Sequencer or module 1050 Mix-Sequencer.
1027 Sequencer This is a 10X3 sequencer with 14 outputs (including 10 separate position/step gates), 6 inputs, buttons for step and reset, and a knobs for pulse repetition/width, which controls the silence between the steps.
1033 Dual Delayed-Trigger Envelope Generator This module is the same as the 1003 ADSR module except it has two more knobs to control gate delay.
1036 Sample-and-Hold / random voltage
1045 Voice Module This all-in-one module contains a VCO, VCF, VCA, and two ADSR envelope generators, as well as 16 inputs, and four outputs. (Note: Most modules feature a spelling mistake “Resanance” instead of “Resonance”.)
1046 quad envelope generator This module is basically a 1003 and a 1033 combined into one module.
1047 Multimode Filter / Resonator This module features 15 inputs, 4 outputs and an overload warning light.
1050 Mix-Sequencer This module features two 4X1 mixers with illuminated on/off buttons.
3001 Keyboard This keyboard features a 5-octave, 61-note (C-C) keyboard with the bottom two octaves (C-B) reverse colored to show the keyboard split. The top half of the keyboard is duophonic. There are separate CV (1v/octave), gate, and trigger outputs for each side of the split, as well as separate panels on either side of the keyboard with controls for portamento, tuning, and pitch interval.
? Dual-Manual Keyboard Two 3001s, one on top of the other, with the bottom octave (C-B) or two octaves (C-B) of the top keyboard reverse colored to show the split.

from ‘The A-Z of Analogue Synthesizers’, by Peter Forrest, published by Susurreal Publishing, Devon, England, copyright 1994 Peter Forrest

ARP 2600
ARP 2600

The ARP 2600 (1971)

Stevie Wonder endorses the ARP 2600
Stevie Wonder endorses the ARP 2600

The 2600 similar to the EMS’s VCS3 was a portable, semi-modular analog subtractive synthesiser with built in modules and, again similar to the VCS3 was designed to target the educational market; schools, universities and so-on. The inbuilt modules could be patched using a combination of patch cables or by using sliders to control internally hard wired connections:

“ARP 2600 The ultimate professional-quality portable synthesizer Equally at home in the electronic music studio or on stage, the ARP 2600 provides the incredible new sounds in today’s leading rock bands The 2600 is also owned by many of the most prestigious universities and music schools in the world Powerful. dependable, and easy to play. the 2600 can be played without patchcords or modified with patch cords. This arrangement provides maximum speed and convenience for live performance applications, as well as total programming flexibility for teaching, research composition and recording. An pre-wired patch connection(s) can be overridden by simply inserting a patchcord into the appropriate jack on the front panel.

The ARP 2600 is easily expanded and can be used with the ARP 2500 series.Renowned for its electronic superiority, the oscillators and filters in the 2600 are the most stable and accurate available anywhere Accompanied by the comprehensive, fully illustrated owner s manual, the ARP 2600 is recognized as the finest, most complete portable synthesizer made today

FUNCTIONS: 3 Voltage Controlled Oscillators 03 Hz to 20 KHz in two ranges Five waveforms include: variable-width pulse. triangle. sine, square, and sawtooth 1 Voltage Controlled Lowpass filter Variable resonance, DC coupled. Doubles as a low distortion sine oscillator. 1 Voltage Controlled Amplifier Exponential and linear control response characteristics 1 Ring Modulator. AC or DC coupled 2 Envelope Generators. 1 Envelope Follower. 1 Random Noise Generator. Output continuously variable from flat to -6db/octave 1 Electronic Switch, bidirectional 1 Sample & Hold with internal clock. 1 General purpose Mixer and Panpot. 1 Voltage Processor with variable lag. 2 Voltage Processors with inverters 1 Reverberation unit. Twin uncorrelated stereo outputs 2 Built-in monitoring amplifiers and speakers, with standard stereo 8-ohm headphone jack. 1 Microphone Preamp with adjustable gain 1 Four-octave keyboard with variable tuning. variable portamento, variable tone interval, and precision memory circuit. DIMENSIONS: Console 32″ x 18″ x 9x Keyboard 35″ x 10″ x 6″ WEIGHT: 58 Ibs”
ARP 2600 Promotional material 1971


ARP 2600 white version
ARP 2600 white version

ARP 2800 ‘Odyssey’ 1972

By the mid-1970s ARP had become the dominant synthesiser manufacturer, with a 40 percent share of the $25 million market. This was due to Pearlman’s gift for publicity – the ARP2500 famously starred in the film ‘Close Encounters of the Third Kind’ (1977) as well as product endorsements by famous rock starts; Stevie Wonder, Pete Townsend, Herbie Hanckock and so-on – and the advent of reliable, simpler, commercial instrument designs such as the ARP 2800 ‘Odyssey’ in 1972.

ARP 2800 Odyssey
ARP 2800 Odyssey

The ARP 2800 ‘Odyssey’ 1972-1981

The Odyssey was ARP’s response to Moog’s ‘Minimoog'; a portable, user-friendly, affordable performance synthesiser; essentially a scaled down version of the 2600 with built in keyboard – a form that was to dominate the synthesiser market for the next twenty years or so.

The Odyssey was equipped with two oscillators and was one of the first synthesisers to have duo-phonic capabilities. Unlike the 2600 there were no patch ports, instead all of the modules were hard wired and routable and controllable via sliders and button son the front panel. ‘Modules’ consisted of  two Voltage Controlled Oscillators (switchable between  sawtooth, square, and pulse waveforms)  a resonant low-pass filter, a non-resonant high-pass filter, Ring Modulator, noise generator (pink/white) ADSR and AR envelopes, a triangle and square wave LFO, and a sample-and-hold function. The later Version III model had a variable expression keyboard allowing flattening or sharpening of the pitch and the addition of vibrato depending on key pressure and position.

ARP 2800 Odyssey Mki
ARP 2800 Odyssey MkI

ARP Production model timeline 1969-1981:

  • 1969 – ARP 2002 Almost identical to the ARP 2500, except that the upper switch matrix had 10 buses instead of 20.
  • 1970 – ARP 2500
  • 1970 – ARP Soloist (small, portable, monophonic preset, aftertouch sensitive synthesizer)
  • 1971 – ARP 2600
  • 1972 – ARP Odyssey
  • 1972 – ARP Pro Soloist (small, portable, monophonic preset, aftertouch sensitive synthesizer – updated version of Soloist)
  • 1974 – ARP String Ensemble (polyphonic string voice keyboard manufactured by Solina)
  • 1974 – ARP Explorer (small, portable, monophonic preset, programmable sounds)
  • 1975 – ARP Little Brother (monophonic expander module)
  • 1975 – ARP Omni (polyphonic string synthesiser )
  • 1975 – ARP Axxe (pre-patched single oscillator analog synthesiser)
  • 1975 – ARP String Synthesiser (a combination of the String Ensemble and the Explorer)
  • 1977 – ARP Pro/DGX (small, portable, monophonic preset, aftertouch sensitive synthesiser – updated version of Pro Soloist)
  • 1977 – ARP Omni-2 (polyphonic string synthesiser with rudimentary polyphonic synthesiser functions – updated version of Omni)
  • 1977 – ARP Avatar (an Odyssey module fitted with a guitar pitch controller)
  • 1978 – ARP Quadra (4 microprocessor-controlled analog synthesisers in one)
  • 1979 – ARP Sequencer (analog music sequencer)
  • 1979 – ARP Quartet (polyphonic orchestral synthesiser not manufacted by ARP – just bought in from Siel and rebadged )
  • 1980 – ARP Solus (pre-patched analog monophonic synthesiser)
  • 1981 – ARP Chroma (microprocessor controlled analog polyphonic synthesiser – sold to CBS/Rhodes when ARP closed)

The demise of ARP Instruments was brought about by disorganised management and the decision to invest heavily in a guitar style synthesiser, the SRP Avatar. Although this was an innovative and groundbreaking instrument it failed to sell and ARP were never able to recoup the development costs. ARP filed for bankruptcy in 1981.

ARP Image Gallery



‘Analog Days’. T. J PINCH, Frank Trocco. Harvard University Press, 2004

‘Vintage Synthesizers': Pioneering Designers, Groundbreaking Instruments, Collecting Tips, Mutants of Technology. Mark Vail. March 15th 2000. Backbeat Books

The rise and fall of ARP instruments‘ By Craig R. Waters with Jim Aikin



3 thoughts on “‘ARP’ Synthesisers. Alan Robert Pearlman, USA, 1970”

  1. I have a couple of the amazing (what became) Fender Chroma Polaris synths (presumed dead in storage). They were analog, but with digital memory & MIDI.
    I wanted to mention, you really should put in a (Tom) Oberheim page, because even before he sold out to Roland or whoever, his was the first portable/reasonable polyphonic synth 4 & 8 note versions), I mean of the known Moog, ARP, etc., that were used in pop, jazz, rock, etc.—at that time (1970s+).
    I also have a tremendous set of PAiA modules that was all the sounds, if monophonic, for pennies on the dollars of other brands. Really PAiA & Aries deserve mention, in that they were affordable (and even kit versions–I was a hobbyist, so built them, but you could buy them already built).

  2. And you know what? Most folks knew ‘ARP,’ the brand of his initials, but not his NAME, Arnold Pearlman. I supposed Bob Moog (and even Buchla & Oberheim, etc.) was luckier to have an odder name.
    I drooled for that stuff, back in the 1970s into the 80s. And in the last decade, many folks are once again getting the musicvirus, that can’t leave your spine, for modular synths. And it’s about time.

  3. My uncle actually used to work in R&D for ARP in the mid 70s, right up until they were bought out by CBS/Fender Rhodes in 1981. He has a ton of working prototypes of both Chroma and Polaris synths in his basement. He also had a great 8 channel keyboard mixer that ARP made called a Performance Series 8…it was a beast of a console for an 8 channel keyboard mixer (about the size of my Allen & Heath MixWizard console…maybe a bit bigger) but it had an onboard graphic EQ for mains and aux outs, and also had a built in bucket-brigade analog delay. After he left ARP, he worked for Rodger’s organs, which was a subsidiary of Roland up until he retired.

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