Birotron B90 (1975–1978)
It has 19 tape players humming beneath a 37-note keyboard. It's a controlled mechanical avalanche.
Overview
The Birotron B90 wasn't built to last. American engineer David W. Biro conceived it and Rick Wakeman of Yes fame bankrolled it. It came out of the same ground as the Mellotron, but it aimed to fix that machine's flaws: tape wear, mechanical fragility, and limited polyphony. Birotronics Ltd. made it between 1975 and 1978. The B90 dropped the Mellotron's complex mechanical tape start-stop system and used electrical switching instead. Rather than moving tape for each keypress, it used solenoid-driven head shifts and fader potentiometers to crossfade between stationary loops. In theory that meant smoother playback and longer tape life. It was ambitious and short-lived, and the timing doomed it.
Wakeman didn't just fund the Birotron. He shaped it. His name appears on a 1980 patent (US 4,182,214) assigned to Birotronics Ltd., which refines the multi-track cartridge mechanism with a common capstan and movable playback heads to give stereo output and better track selection. The instrument turns up on his 1977 solo album *Criminal Record*, on Yes's 1978 release *Tormato*, and on the live recordings compiled on *Yesshows*, where its orchestral textures colored tracks like "Don't Kill the Whale." Tangerine Dream and Earthstar also reportedly used it, drawn to its ability to layer real instrument recordings with real-time control.
The B90 was a creature of its moment, and that moment passed quickly. Only 13 units were ever produced. By 1979, Birotronics Ltd. had collapsed. Poor design wasn't the cause. Affordable polyphonic synthesizers and early digital samplers arrived and offered comparable sounds without the mechanical complexity, maintenance headaches, or bulk. The B90 became a footnote, and a handful of surviving units are what's left.
Specifications
| Manufacturer | Birotronics Ltd. |
| Model | B90 |
| Type | Electro-mechanical keyboard instrument, tape loop keyboard |
| Production years | 1975–1978 |
| Keyboard | 37-note keyboard |
| Sound source | 19 independent 8-track cartridge players |
| Sound selection | Each cartridge providing up to four selectable sounds distributed across two keys |
| Controls | Real-time control via knobs for volume, attack, decay, and pitch |
| Tape format | Endless magnetic tape loops stored in 8-track cartridges |
| Tape length | Approximately 10 minutes of tape per cartridge |
| Tape speed | Standard 8-track cartridges operated at 3¾ inches per second |
| Original price | Around £1,000 each |
Key Features
19 Independent 8-Track Cartridge Players with Electrical Switching
On the Mellotron, pressing a key physically started a tape strip moving. The B90 kept its 19 cartridges running continuously. Each cartridge held an endless magnetic tape loop, and when a key was pressed, the system electrically routed the appropriate playback head's signal to the mixer. That removed the mechanical wear from repeated start-stop cycles and allowed longer, uninterrupted playback. The design, patented in 1977 (US 4,018,127), relied on solenoid-driven head shifts and fader potentiometers to transition smoothly at tape splices. That avoided audible clicks or dropouts during sustained notes.
Movable Playback Heads and Common Capstan Mechanism
A later refinement, detailed in a 1980 patent co-invented by Rick Wakeman, added a common capstan shared across tracks within a cartridge. This improved tape stability and synchronization. The movable playback heads allowed selection of different tracks on the same cartridge, which gave stereo output and more flexible sound layering. It was a significant step up from fixed-head systems, with greater control and sonic depth and no extra mechanical complexity for each voice.
Real-Time Knob Control for Volume, Attack, Decay, and Pitch
Many tape-based keyboards of the era offered fixed envelopes. The B90 gave players real-time control over volume, attack, decay, and pitch via front-panel knobs. That made it unusually expressive for a tape-replay instrument.
Historical Context
The B90 was born in the mid-1970s as a direct response to the Mellotron's limitations, and it represented the pinnacle of tape-based keyboard technology. According to SynthDB, it attracted interest from major musicians of the era, who liked its orchestral realism, its real-time control, and, despite conflicting reports, claims of a lighter weight and more compact size. Its development also coincided with the dawn of digital sampling and polyphonic synthesis. Instruments like the Fairlight CMI and Prophet-5 offered comparable sounds with far greater reliability and flexibility, which made the B90 obsolete almost as soon as it arrived. With only the B90 in its lineup, Birotronics Ltd. had no fallback when the market shifted, and the company folded in 1979.
Collectibility & Value
Only 13 units were ever built, and Birotronics destroyed prototypes and specialized spare parts after bankruptcy. That makes the B90 one of the rarest instruments in progressive rock history. By the 2010s, only a handful were known to exist, and reports from 2015 suggest as few as two remained functional. Multiple sources, including Facebook groups and Reddit discussions, have called it "music's rarest instrument." In 2011, Rick Wakeman reportedly offered his personal B90 for between $1,500 - a figure that, if accurate, seems astonishingly low given its scarcity, though it may reflect the instrument's unreliability and lack of serviceability. Collectors are warned that some software libraries claiming to emulate B90 woodwinds may be misleading, as no such recordings were ever made for the instrument.
Similar items on eBay
No exact Birotron B90 listings are live right now — these searches show current Birotron and similar vintage synth gear on eBay:
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.