Kristin and I recently covered a Ben Folds song for our song-a-week blog called "You Don't Know Me". I was trying to figure out how he had made the brass & strings, which had a decidedly "sampley" sound to them, and I suddenly decided that it must be a Mellotron.
The Mellotron is an ingenious instrument; an analogue, electro-mechanical "sampler" that uses strips of pre-recorded magnetic tape to reproduce the sound of actual instruments. Each key has its own little magnetic playback head, and a strip of tape with 3 tracks of audio on it; say, flute, guitar and organ. You press down a key, and the tape strip begins to play a sample of that instrument playing the corresponding note. When you let go of the key, the tape strip springs back to the beginning and waits for the key to be pressed again. Each strip of tape is 8 seconds long.
Probably the most recognizable occurrence of the Mellotron in popular music is the eerie flute sound used in the Beatles' "Strawberry Fields Forever".
Candor Chasma goes into great detail of the inner workings and various models of the Mellotron. And the guys at Streetly Electronics (Mellotron repairmen!) offer numerous samples of Melltron sounds for your listening pleasure.
In the DIY world of circuit-bending, we have the Melloman, built by Mike Walters, which uses 14 walkmans mounted in a beautifully designed chassis.
It turns out that no Mellotron was used in the making of "You Don't Know Me", but I found this out too late to prevent me from having so much fun.