Name that tune

[simont]

The following tune has been wandering occasionally around my head for some months if not a year or so, and I've no idea what it is, and it's really bugging me that I can't remember.

It took me some faffing to get this into a suitable format; I actually ended up with several suitable formats. So here we go. I've got a MIDI file (very small to download, and Windows Media Player ought to cope): http://www.tartarus.org/~simon/20051107-name-that-tune/tune.mid. Just in case that doesn't work for everyone, here's an MP3 version (larger, but ought to get the job done): http://www.tartarus.org/~simon/20051107-name-that-tune/tune.mp3. And finally, for those without sound or who prefer to do these things visually, here's the tune written down:

(I don't have absolute pitch, so I've transposed it into C for minimum sharps-and-flats hassle. People who do have absolute pitch should not take this as indicating anything whatsoever about the key the real thing is in.)