If you look at how this keyboard actually works, it is an amazingly complicated sample playback machine. Wicked cool.
The Mellotron is an electro-mechanical, polyphonic keyboard originally developed and built inBirmingham, 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 It superseded the Chamberlin, which was the world's first sample-playback keyboard.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.