The Mellotron is an electro-mechanical musical instrument developed in Birmingham, England, in 1963. It evolved from the similar Chamberlin, but could be mass-produced more efficiently. The instrument is played by pressing its keys, each of which pushes a length of magnetic tape against a capstan, which pulls it across a playback head. Then as the key is released, the tape is retracted by a spring to its initial position. Different portions of the tape can be played to access different sounds.
The first models were designed to be used in the home and contained a variety of sounds, including automatic accompaniments. Bandleader Eric Robinson and television personality David Nixon were heavily involved in introductory promotion of the instruments. A number of other celebrities such as Princess Margaret were early adopters. The instrument began to be used by rock and pop groups in the mid to late 1960s. The Moody Blues's keyboardist Mike Pinder used it extensively on the band's 1967 orchestral collaboration Days of Future Passed. The Beatles used the instrument on several tracks, including the hit single "Strawberry Fields Forever". The Mellotron was subsequently used by groups like King Crimson and Genesis, becoming a common instrument in progressive rock. Later models, such as the best selling M400, dispensed with the accompaniments and some sound selection controls so it could be used by touring musicians. The instrument's popularity declined in the 1980s after the introduction of polyphonic synthesizers and samplers, despite a number of high-profile users like Orchestral Manoeuvres in the Dark and XTC.
Production of the Mellotron ceased in 1986, but it regained popularity in the 1990s and was used by several notable bands, such as Oasis and Radiohead. This led to the resurrection of the original manufacturer, Streetly Electronics. In 2007, Streetly produced the M4000, which combined the layout of the M400 with the bank selection of earlier models.