Oberheim Matrix-12 (1985–1988)

Twelve voices, a 16-slot modulation matrix, and a price tag that could have bought a used car - Oberheim's last great analog statement.

Overview

At 45 lbs and 38.5 inches across, the Matrix-12 sits on a stand like laboratory equipment with a keyboard bolted to the front. Oberheim built it in the United States during a three-year window from 1985 to 1988 and priced it at $5,995. That put it out of reach for most players and squarely in the territory of studios and touring professionals who needed something nobody else had.

For that money you got twelve fully polyphonic analog voices. Each voice has two digitally controlled oscillators, four ADSR envelopes, and two LFOs. The oscillators cover sine, triangle, sawtooth, square/pulse, and noise. Because they are digitally controlled rather than voltage-controlled, they stay in tune in a way earlier analog polysynths couldn't manage. Players who had fought drifting oscillators on stage for years suddenly had an instrument that held pitch through a full set.

The filter carries the SEM lineage forward. It's a 12dB/oct resonant low-pass with a frequency range of 10Hz to 20kHz, switchable to a steeper 24dB/oct slope. The gentler slope gives the singing, vocal quality Oberheim had built its reputation on. The steeper setting lets the instrument punch through a dense mix without getting buried.

The feature that defined the Matrix-12 was its modulation matrix. It has sixteen slots, real-time assignable, and can route any of 32 sources to any of 64 destinations with adjustable scaling. LFOs, envelopes, velocity and aftertouch are all available as sources. Pitch, filter, pulse width and pan are all available as destinations. Modern Recording (September 1985, p.49) described the instrument as a MIDI-programmable synthesizer based on the Oberheim Xpander, controlling twelve independently programmable voices.

Key Features

16-Slot Modulation Matrix with 32 Sources and 64 Destinations

The modulation matrix was the architectural decision that made the Matrix-12 what it was. With sixteen slots available simultaneously, a player could route aftertouch to filter resonance, LFO rate, and oscillator sync depth all at once, each with its own scaling amount. In 1985, nothing else in a keyboard instrument offered this level of routing flexibility. Period coverage in Modern Recording (February 1985, p.2) framed the instrument around what it called twelve of the most amazing voices, paired with a velocity keyboard.

Dual DCOs per Voice with Hard Sync, Soft Sync, and Cross-Modulation

Each of the twelve voices carries two digitally controlled oscillators capable of hard sync, soft sync, and cross-modulation. Pulse width can be modulated by LFOs, envelopes, or even other oscillators. The digital control keeps tuning rock-stable, while the analog signal path keeps the warmth and slight imperfection that made the instrument desirable in the first place.

SEM-Style Filter Switchable Between 12dB/oct and 24dB/oct

The filter delivers what Oberheim's earlier instruments were known for - a creamy, singing resonance at the gentler 12dB/oct slope. Switching to 24dB/oct gives the Matrix-12 an authority the older designs lacked. The unbalanced 1/4" audio input feeds the filter, so it can process external signals. That means the instrument can color anything fed through it, not only what the keyboard plays.

Four ADSR Envelopes and Two LFOs per Voice

Four envelopes per voice, each independently assignable to amplitude, filter, pitch, or modulation depth. Two LFOs per voice with sine, triangle, square, sawtooth, and sample & hold waveforms. Most contemporary polysynths offered one or two envelopes total. The Matrix-12 gave you four per voice, across twelve voices.

76-Key Keyboard with Velocity and Channel Aftertouch

The keyboard spans 76 keys with velocity sensitivity and channel aftertouch across the full range. Aftertouch is integral to how the instrument plays. Press harder after striking a key and the modulation matrix can respond with filter sweeps, vibrato, patch morphing, or whatever the player programmed.

100 User-Programmable Patches

Memory holds 100 patches, all user-programmable. In 1985, that was a meaningful amount of storage for an analog instrument.

Historical Context

The Matrix-12 arrived in 1985, a year when many people were declaring analog synthesis dead. The Yamaha DX7 had taken the world by storm with its digital FM synthesis, offering pristine electric pianos and metallic textures at a fraction of the cost. Polyphonic analog synths like the Sequential Prophet-600 were struggling to compete on price and reliability. Oberheim built on the legacy of the OB-Xa and the experimental Xpander - a nearly identical engine in a rack format released a year earlier - and doubled down on analog.

Programming takes patience, a manual, and a willingness to get lost in menus. The payoff is sonic depth that feels almost orchestral. Its modulation matrix concept was later borrowed by synths like the Access Virus and Waldorf Microwave. Software synths like Arturia's Matrix-12 V also exist to capture its sound.

The rackmount sibling, the Matrix-12R, arrived in 1987 and traded in a similar price range, though it lacked the keyboard's expressiveness. Artists who gravitated toward the Matrix-12 included Vince Clarke of Erasure, Howard Jones, and film composers such as Brad Fiedel, who used it on the Terminator score. The instrument was noted for evolving, textured pads, searing leads, and percussive stabs that felt alive.

Collectibility & Value

Fewer than 1,000 units were reportedly produced during the 1985-1988 run, which explains why the Matrix-12 rarely appears on the used market. A fully functional unit in good condition commands between $4,000 and $7,000, with mint examples sometimes exceeding $8,000. The Matrix-12R is slightly less common and trades in a similar range. A recent eBay listing observed an asking price of $19,995 for an original vintage USA unit, which is an outlier.

Buyers should know the common failure points. Capacitor leakage is a known issue, and many units have been or need to be recapped. Power supply failures are typical of aging electronics from this era. The keyboard is sturdy but can suffer contact wear, especially in heavily used units, so test every key for velocity and aftertouch response. A working Matrix-12 should feel like a precision instrument: buttons click crisply, the display is clear, and patches recall reliably.

A service manual is available via archive.org, which helps. Repairs still aren't a casual DIY job. The modulation matrix alone involves enough digital control that you need proper documentation to troubleshoot it.