Okay, so pretty much everybody's already heard this: the original Doctor Who theme from 1963. But, really, ain't it just goddamned amazing that anyone was able to produce a piece like this back then? Seriously, check it out, and try to imagine how it was possible.
Turns out, it was possible because the BBC Radiophonic Workshop hired an electronic music pioneer named Delia Derbyshire. The theme itself was composed by Ron Grainer--complete with unusual notations about "sweeps", "swoops", "wind clouds", and "wind bubbles"--but actually produced by Derbyshire. The final piece was all electronically-produced sounds, but this was the era before synthesizers, so she produced it all with electronic oscillators and other arcane gear, and assembled them all by physically splicing together bits of audio tape. Grainer was apparently so amazed and impressed with the result that he tried to get the BBC to Derbyshire credit--and royalties--as co-composer.
Anyway, she's also done a bunch of other cool, weird, atmospheric stuff, and you can download some of it at this site. It's very much worth checking out, especially "Dreams" and "Moogies Bloogies".