The infamously rare Birotron B90.
The back of the unit, displaying the use of individual tapes.
The Birotron was a keyboard instrument created by David Biro in the 1970s as a low-cost alternative to the Mellotron. The primary difference between the two, aside from the cost, is the Birotron's use of 8-track tape loops, thus allowing sounds to be played indefinitely, as opposed to the Mellotron's use of standard magnetic tapes and its eight-second playback limit. The instrument has been used by such noted artists and bands as Keith Emerson, Elton John, John Lennon, Paul McCartney, The Beach Boys, Rod Stewart, Led Zeppelin, Patrick Moraz, Chicago, Larry Fast, Tangerine Dream, Klaus Schulze, and Rick Wakeman, the latter of whom also helped fund David Biro's production company, Birotronics. Despite this initial success, the Birotron was ultimately brought down by frequent production shortages, a lack of consistent funding, and poor timing.
An entire library of sounds was recorded for use on the Birotron, one of which - the church organ - was reportedly recorded by Rick Wakeman himself. It is unknown, however, how many of these recordings were actually put to use, and many are now believed to be lost due to the degradation of the tapes. The Birotron itself is considered to be perhaps the rarest keyboard instrument in existence, as less than fifty units were ever manufactured, most of which are no longer functional. David Biro lost his own unit following the bankruptcy of Birotronics and the subsequent repossession of his home in Yalesville, Connecticut. Despite countless attempts to rescue the Birotron, it is currently believed that there is no surviving instrument with a complete, fully-functional, undamaged tape set.