The Moodies were a very big user of the mellotron and it was an intrinsic part of their unique sound back in the late 60's. It's a keyboard instrument designed to imitate sounds that you couldn't get from a keyboard in those days; strings, choirs, flutes and so forth.

It works with tape technology; under each key there's a tape head, a strip of prerecorded magnetic tape and a lot of gears and pulleys. When you press a key, the mechanism runs the tape by the tape head and plays a "sample" of an orchestra playing, say, an E-flat. When you release the key, the tape rewinds. Mechanically it's absolutely dreadful but it sounds beautiful.

For all practical purposes the Mellotron is a sampler; it plays back recorded sounds but it cannot record. The interesting limit is that you can only hold a note for as long as the piece of tape will let you. This maxed out at about 8 seconds, after that it just stopped playing. Mike Pinder's style of keyboard playing, as lush as it comes across, is actually made up of many shifting notes. Thus, he could never hit a chord and hold it for 16 bars in a slow tempo. Without a doubt, he is one of the few who really mastered this kind of a technique.

Also note the keys of the Mellotron are individually pressure sensitive, so you can control the way individual notes fade in and out. How hard you press a key affects the pitch of the note. It's possible to play two notes of a chord "in tune," and a third note "out of tune." An expert player has to have a very sensitive playing style, and take great care to keep the pitch on an even keel.

"Legend of a Mind" is a very fitting example of the other "feature." There is a knob that changes the pitch of every key and in "Legend of a Mind," Mike Pinder uses it extensively:

    "...no, no no no, he's outside (BEND!), looking in (BEND!) (BEND!)"

and just before the last verse, there is more bending. In each of these, a note or chord is struck and then the pitch is "bent" by turning this knob. This is '60s technology and involves actually changing the speed of the motor that drives the tape mechanism and is imprecise. It has to be played by ear, rather like a slide-whistle. And there's the problem. The knob has a marked "scale" that indicates when the pitch has been returned to "neutral" or "normal" but it too is not very accurate. So the player has to determine by ear how much "bending" is enough and how much "bending" back to "normal" pitch is enough. This is very demanding of the player, who has to constantly listen to stay "in tune."

Mellotron is still being used but synthesizers have mostly replaced them. They went out of production years ago; the technology was a lot less reliable than electronic signal generation, as with modern synthesizers. Mellotrons have a lengthy warm-up period, during which they exhibit pitch shifts. After 30 minutes or so of warming up, they stabilize somewhat but are still, well, "moody." And so, with their bulkiness, delicacy, scarcity and quirks, they're almost extinct. However, the Mellotron sounds have been sampled and are currently being produced by synthesizers.