A tape-based sample playback synthesizer similar in concept to the Mellotron. Dave Biro developed the instrument in the early 1970s (with funding from, among others, Rick Wakeman), as an attempt to overcome some of the limitations and reliability problems of the Mellotron. Instead of the strips of tape used in the Mellotron, the Birotron used commercially available 8-track cartrides, which contained continuous loops of tape. The Birotron was capable of reproducing up to four stereo instrument sounds per set of cartridges, as opposed to the 3-track mono capability of most Mellotron models.
Because the tapes ran continuously, a keypress could occur at any point in a tape loop. This meant that unlike the Mellotron, the Birotron was not capable of reproducing the natural attack transient of the recorded instruments (for example, the breath "chiff" at the beginning of a flute note). Birotronics Ltd. tried to overcome this by equipping each note mechanism with VCA and envelope generator circuits; however, this became one of the items that drove the cost up. Ultimately, Birotronics was unable to sell the instruments due to delays in funding, and the increasing market for chip based synths.
Most reliable estimates indicate that about thirty Birotrons were built, or parts existed to build thirty. Wakeman featured one on the Yes album Tormato.