Made to Be Seen, Not Just Heard

Cherry Audio's Pentaphonic synthesizer is a breathtaking virtual instrument that revives one of the rarest synthesizers ever made: the 1981 Pentaphonic by Gleeman Instruments. With fewer than 70 units ever produced, this synthesizer is legendary for its rich tone, distinctive design, and pioneering sequencing capabilities.

To honor both its sound and aesthetics, we have expertly replicated the thick, rich sound quality of its unique DCO (digitally controlled oscillator) and analog filter architecture, ensuring that the essence of the original is fully realized. Our visual makeover offers a choice of stunning designs inspired by the various looks it sported during its brief existence.

Beyond preserving every original option, we have dramatically expanded its capabilities in ways previously unimaginable. Cherry Audio's Pentaphonic synthesizer is not just an emulation of a lost classic; it is a celebration of the innovative spirit behind the original, proving that the most groundbreaking ideas don't always come from the biggest names.

Gleeman Pentaphonic - The Ultimate Portable

In the early 1980s, while Silicon Valley focused on personal computers, brothers Bob and Al Gleeman were working in a Mountain View garage on a portable polyphonic synthesizer designed to hold its tuning under stage lights. Al, an electrical engineer, handled the design, while Bob, a musician, managed the business, creating a unique instrument that would stand out in a market filled with analog polysynths like the Prophet-5 and Memorymoog.

The Gleeman Pentaphonic featured five voices (hence "penta") with fifteen DCOs using a pair of Intel 80186 microprocessors to ensure precise tuning that analog models couldn't match. Each oscillator offered eight waveforms, including two harmonically rich "complex" waveforms. These were low-resolution, 32-sample waveforms played back at a variable clock/sample rate. A single digital low-frequency oscillator (LFO) handled triangle wave-based modulation for tremolo and vibrato. The synthesizer's rich hybrid sound came from its Curtis CEM 3320 4-pole (24 dB per octave) low-pass resonant voltage-controlled filter (VCF) and the CEM 3360 dual voltage-controlled amplifier (VCA).

The first Pentaphonic arrived in 1981 in a plain black chassis with an integrated handle and built-in speaker, an "ultimate portable" weighing just 18 pounds. Underneath sat a hands-on control panel, a 37-note keybed, a 300-note real-time polyphonic sequencer, computer-tuned chorusing, and a joystick for pitch. At under $3,000, it went head-to-head with the Prophet-5 at $4,600, offering tuning stability its analog rivals couldn't achieve. They handmade around 30 black units with various, evolving features.

When a transparent version was suggested, Gleeman Instruments developed the Pentaphonic Clear. This model featured a clear acrylic housing, plexiglass knobs, and optional lighting that allowed audiences to see the circuitry illuminated against the green circuit boards. It came with a shoulder strap, a remote power supply to reduce weight, and a 20-foot cable, making it a fully equipped stage keytar. The Clear also brought the "Presetter" upgrade with 100 programmable patch memories, a two-axis joystick for simultaneous pitch and mod, an improved chorus, and a 600-note sequencer. Fully loaded, it was priced around $3,400. Fewer than 20 Clears were ever built.

The Gleeman Pentaphonic remains renowned for its rich, powerful, crystal-clear sound. Its exceptionally thick pads and string patches can make instruments like the OB-Xa sound thin by comparison, while delivering a sound reminiscent of a Memorymoog with remarkable clarity. The Complex 1 and Complex 2 oscillator waveforms produced bright, bell-like overtones, akin to Frequency Modulation (FM) synthesis, years before the DX7. However, the Pentaphonic lacked the grit and experimental features of its analog competitors, and its absence of an oscillator sync mode limited its sonic flexibility. Additionally, some performers found its 37-key range and lack of touch sensitivity restrictive. As the market shifted toward digital synthesizers in the mid-80s, the Gleemans wound down Pentaphonic production. In 1994, David Kean of the Audities Foundation bought the brothers' remaining parts inventory and assembled a small batch of new units — reportedly seven fresh Pentaphonics and seven Clears — keeping the flame alive for collectors.

Despite its scarcity, the Pentaphonic found its way into some notable hands. Jazz legend Oscar Peterson was so captivated by its sound that he bought a Clear immediately. Kevin Gilbert used one early in his career on the album NRG. The Moog Cookbook, Kansas, The Band, and R.E.M. put the Pentaphonic to work, and Depeche Mode's Martin Gore is counted among the owners. Surviving units surface rarely, and the Clear especially remains one of the most recognizable synths of its era.

Cherry Audio Pentaphonic - Born for the Spotlight

In the pioneering spirit of the small, ambitious outfit that built something genuinely unique for its time, Cherry Audio has embraced the challenge of actualizing the unrealized Gleeman prototype said to have been conceived in 1983. This successor was planned to feature eight voices, a 61-key keyboard, enhanced sequencer capabilities, and integrated MIDI support. With the introduction of Cherry Audio's Pentaphonic synthesizer, we've taken this concept beyond what was possible at the time while preserving the original design's unique qualities.

We have included three UI themes to capture the Pentaphonic's full chronology: the standard black look, plus stunning transparent and "Audities" clear themes with click-and-drag opacity. Polyphony (including unison with detune) has expanded to 2-16 voices, and we've also added retrigger and note priority to monophonic mode.

We added pulse width modulation to each oscillator, introduced a noise generator, and implemented oscillator sync. We also added an additional LFO, and each now includes all eight waveforms found in the DCOs: Complex 1, Complex 2, 3% Pulse, 12% Pulse, 50% Pulse, Ramp, Triangle, and Sine.

We've expanded the 4-pole (24 dB per octave) low-pass filter with a 2-pole (12 dB per octave) mode and keyboard tracking, and the amplifier section now includes a limiter. We've also introduced true performance expression to Pentaphonic, including velocity, channel and polyphonic aftertouch, and 14 parameters that can be modulated through keyboard pressure.

The advanced arpeggiator and 16x4 programmable polyphonic step sequencer are both syncable and transposable. They offer flexible humanization settings for patterns and sequences that surpass the original hardware. Additionally, it features a Parameter Animator that can be routed to cutoff, resonance, oscillator pitch mod, and oscillator gain. Alongside the original chorusing effect, Pentaphonic now includes a global effects chain with 22 studio-quality, modulatable effects to choose from.

Cherry Audio has teamed up with Mike Martin to produce an introductory video for Pentaphonic. This deep dive highlights its standout features, including its unique oscillators and waveforms, the three UI themes, expressive performance features, and all the ways Cherry Audio has expanded upon the original Gleeman Pentaphonic.