Wikipedia
The Birotron (pronounced By-ro-tron) is a tape replay keyboard conceived by Dave Biro of Yalesville, Connecticut, US, and funded by Rick Wakeman of the progressive-rock group Yes, and Campbell Soup Company- Pepperidge Farm Foods in the mid-late 1970s.
A Mellotron-like instrument in the prototype stage, and intended for mass production - it was featured on a hit single and used on several albums and tours. It appeared in advertisements and received press in several newspapers as the next 'latest and greatest' keyboard instrument. It also received over 1000 advance orders from many prominent musicians worldwide, including members of the Beatles and Led Zeppelin.
Despite this success, it is now generally considered the world's rarest keyboard instrument in the genres of pop/rock music. It also retains the highest selling price for any Mellotron related keyboard, and since its inception, has been one of the most difficult to find, seldom seen, and least recorded instruments in the entire world.