Caught this awsome video over at Music Thing:
I'm just really impressed with the low latency they managed to squeeze out of such a rube goldberg device.
From Mellotron article at wikipedia:
The Mellotron (along with its direct ancestor the Chamberlin) was, in effect, the world's first sample-playback keyboard. The heart of the instrument is a bank of magnetic tape strips (these tapes were parallel linear, not looped as has sometimes been reported or presumed), each tape with approximately eight seconds of playing time; playback heads underneath (but not directly underneath) each key enables performers to play the pre-recorded sound assigned to that key when pressed.