Mellotron

The Mellotron is an electro-mechanical, polyphonic keyboard originally developed and built in Birmingham, England in the early 1960s. It superseded the Chamberlin, which was the world's first sample-playback keyboard. The heart of the instrument is a bank of parallel linear magnetic audio tapes, which have approximately eight seconds of playing time each. Playback heads underneath each key enable the playing of pre-recorded sounds.

The earlier MKI and MKII models contained two side-by-side keyboards: The right keyboard accessed 18 "lead/instrument" sounds such as strings, flutes, and brass; The left keyboard played pre-recorded musical rhythm tracks in various styles.

The tape banks for the later, lighter-weight M400 models contain only three selectable sounds including (typically) strings, cello, and an eight-voice choir. The sound on each individual tape piece was recorded at the pitch of the key to which it was assigned. To make up for the fewer sounds available, the M400 tapes came in a removable frame that allowed for relatively quick changes to new racks of sounds.