Image: Robert Brook, CC BY 2.0 — via Wikimedia Commons
Oberheim Polyphonic
| Category | Electronic (polyphonic analog synthesizer) |
|---|---|
| Country of origin | USA |
| Classification | analog synthesizer |
| Wikipedia | en.wikipedia.org |
| Wikidata | Q7074739 |
Overview
The Oberheim Polyphonic refers to the family of polyphonic analog synthesizers Tom Oberheim built in the mid-1970s by combining multiple Synthesizer Expander Modules (SEMs) under a single shared keyboard. The series began with the Two-Voice in 1975, followed by the Four-Voice and the Eight-Voice. Each SEM is a complete monophonic synthesizer with two oscillators, a state-variable filter, two envelopes, and an LFO; assembled together they formed the first widely available commercial polyphonic synthesizers.
Origin & History
Tom Oberheim founded Oberheim Electronics in 1969 as a maker of effects and add-on devices, and released the SEM in 1974 as a small voice module to be added to existing synthesizers. The Two-Voice arrived in 1975 by mounting two SEMs and a small sequencer onto a single keyboard chassis; the Four-Voice followed almost immediately. By the late 1970s the polyphonic line was overtaken by the OB-X family, which used internal voice cards and integrated patch storage. Original Two-Voice and Four-Voice instruments are now sought-after vintage units.
How It’s Played
Each SEM in the system is programmed independently, so the player creates a polyphonic sound by setting all SEMs to the same patch — or by deliberately leaving them slightly different. A keyboard assigner distributes incoming notes to free voices. The Four-Voice’s keyboard handles voice allocation automatically; performers playing complex parts often arranged the SEMs by hand for layered or split textures.
Cultural Significance
The Oberheim Polyphonic was the first commercial polyphonic analog synthesizer and a defining instrument of mid-1970s electronic music and progressive rock. Its modular architecture also influenced later polysynth design and contributed to the lasting reputation of the SEM voicing.
Related Instruments
- Oberheim OB-X – successor with internal voice cards
- Oberheim OB-Xa – mid-line OB family member
- Oberheim OB-8 – production successor in the series
- Oberheim OB-1 – early Oberheim monosynth
- Sequential Circuits Prophet-5 – the polysynth that succeeded it commercially
Frequently Asked Questions
How was the polyphonic line built?
By combining multiple SEM modules under a single keyboard with a voice assigner.
How many voices were available?
Two, four, and eight, depending on the model.
Did the polyphonic series have patch memory?
No — programs were set by adjusting the knobs of each SEM directly.
