by Dave Spiers
After the success of the monophonic SEM released in 1974, such was the demand for polyphonic synthesisers that Tom Oberheim had the idea of chaining together multiple SEMs and triggering them via a polyphonic keyboard developed by Dave Rossum of E-mu Systems.
As a consequence, the Oberheim Two-Voice and Four-Voice instruments were released in 1975 and followed in 1977 by the magnificent Eight-Voice. The latter marked the pinnacle of the SEM based synthesisers and while all SEM based instruments were hugely successful, because each SEM had to be individually set up, the Four-Voice and Eight-Voice were somewhat unwieldy - especially if you wanted to create a uniform polyphonic sound across each note. Additionally, there was the issue of storing your patches, which being blunt, was a fudge on both of these instruments.
Oberheim 8 Voice
A solution to polyphony, elegant patch storage and simple, ergonomic work-flow was realised by Dave Smith with the game changing Prophet 5 synthesiser, released in 1978.
Consequently it was embraced by synth players the world over and Oberheim found itself facing a sharp decline in sales of Four and Eight-Voice instruments.
“As we got into the latter part of 1978, sales of the four and eight voice were dropping like a big stone, due to the fact that the Prophet 5 was coming out in quantity.”
Recounts Tom Oberheim in the Bright Sparks Documentary.
Knowing he had to act fast to save the company, with ace engineer Jim Cooper, Tom set to work on the OB-X, a polyphonic synth which used the same one set of controls for each voice paradigm, and incorporated the same patch storage method as the Prophet 5.
“When we first exhibited OB-X at the 1979 NAMM show, I knew that if it didn’t get some acceptance we’d probably be out of business. That night I went to my hotel room, but because I couldn’t sleep I went to the lobby of the hotel and I wrote the owners manual. The next day, by noon, we knew were fine because we wrote somewhere between half million, and a million dollars worth of business.”
OB-X was available in 4, 6 or 8 voice configurations, and featured a SEM based 2 pole VCF lowpass filter with a dedicated four-stage envelope. It also contained two VCOs, a four-stage VCA envelope, a comprehensive LFO section, polyphonic portamento and 32 patch locations.
It also had Cross Modulation which gave it a huge range of sound possibilities, exemplary examples of which can be heard by David Sylvian’s use of the OB-X on the Japan album, Tin Drum. Other users included Billy Currie of Ultraxox, BBC Radiophonics Workshop, Chick Corea, Herbie Hancock, Depeche Mode, Queen, Larry Dunn, Youth, Chris Franke, Styx and many more.