The Oberheim Polyphonic Synthesizer is a series of analog music synthesizers that was produced from 1975 to 1979 by Oberheim Electronics. Developed by Tom Oberheim, they were the first production synthesizers capable of playing chords.

Background<span class="anchor" id="SEM"></span>

After Oberheim introduced the DS-2 digital music sequencer, Tom Oberheim recognized that customers wanted to play one synthesizer while the DS-2 played a sequence on another, or layer the sound of one synthesizer with another. To address this need, he introduced the Synthesizer Expander Module (SEM), a semi-modular analog synthesizer module, in 1974. The SEM featured two VCOs and a two-pole voltage-controlled filter that could operate as a low-pass, high-pass, band-pass, or band-reject filter, giving it a different sound from the Moog and ARP four-pole low-pass ladder filters popular at the time.

Specification

In late 1975, after Norlin canceled several large Maestro orders, Oberheim developed a series of polyphonic synthesizers by combining multiple SEMs with a digitally-scanned keyboard developed by Dave Rossum and a two-channel sequencer. By packaging two or four SEMs, each capable of generating one voice (or note), together under keyboard control, he was able to create synthesizers that could play two or four notes simultaneously.

In 1977, the Oberheim Eight Voice (EVS), available with either a single or dual manual keyboard, was added to the series. <br/>exhibited at Musical Instrument Museum (Phoenix)

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The SEM, Two Voice, Four Voice, and Eight Voice were eventually replaced by a series of microprocessor-controlled synthesizers, beginning with the OB-1 and culminating in the OB-X and OB-Xa, which were fully programmable and significantly more compact than their predecessors, which Oberheim discontinued production of in 1979.

Notable users

thumb|right|300px|The first prototype of the Oberheim Four Voice, as used by Stevie Wonder. The front panel still shows the [[braille labeling.]]

  • 808 State
  • Akiko Yano
  • Blue Weaver (Bee Gees)
  • Bob James
  • The Brothers Johnson
  • Chick Corea
  • Christine McVie (Fleetwood Mac)
  • Christopher Franke
  • Dave Greenfield (The Stranglers)
  • Dave Grusin
  • Dee Palmer (Jethro Tull)
  • Depeche Mode
  • Jimmy Jam and Terry Lewis
  • Larry Dunn (Earth, Wind & Fire)
  • Laza Ristovski
  • Lyle Mays (Pat Metheny Group)
  • Vangelis
  • Vince Clarke

Software emulations

GForce Software collaborated with Tom Oberheim and former Oberheim engineer Marcus Ryle to develop the GForce Oberheim OB-E, a software synthesizer emulation of the Eight Voice,