I spoke to Don recently on FB and he said the following:
The following is not remotely ambient or IDM, but it's pretty important in the history of electronic music. 22 years ago today, the KLF released a unique mix of one of their most famous tracks, under the name The Justified Ancients Of Mu Mu. They pressed a very small number copies on a single-sided gray 12" and never re-released it any form. In the vinyl era, and in fact until quite recently this version was was complete unobtanium. Copies still change hands for hundreds of dollars. Miraculously, it has never been bootlegged. Thanks to a well-connected friend of mine, I have a FLAC of a vinyl rip done with considerable skill. All of this would be moot if the song was lousy, but as it turns out it's a bit of a timeless masterpiece. The Original Club Mix is deceptively simple, oppressively dark and does not remotely resemble what UK 'ardcore rave music sounded like at the time. To really appreciate it, one must hear it on a HUGE sound system, preferably at an illegal party in a dingy warehouse. Failing that, a good pair of headphones will suffice. The theme of the track, the economic and urban decay of the northern cities in the UK, is of course irrelevant in today's world. Oh, wait...
Grooveshark version, which has much higher quality audio.
http://www.youtube.com/watch?v=96nBBHvq4bM