How do DJs manage to create "Remixes" that sound totally unlike the original song?

Recently, I was comparing The Beastie Boys’ song Body Movin’ with the remixed version by FatBoy Slim. The FatBoy Slim version is, IMHO, an infinitely better song- but it’s also being sung at a totally different tempo, pace, etc. It’s so completely different from the original version I’ve still never managed to work out how the lyrics changed to fit the remixed beat and backing track. If I didn’t know any better, I’d say that Mr. Slim actually got the Beastie Boys back into the studio to re-record the lyrics, so different is the pacing, tone, etc of the song.

This isn’t the first remix I’ve noticed this on, though- there are a few others I’ve heard over the years (none I can specifically recall the names of off the top of my head, alas) where the remix is so completely different from the original I don’t see how it could have been done without a complete re-recording with the aid of the original artists.

Anyone know how they manage to change the songs so much without actually re-recording the whole song in a totally different manner?

There are programs out there that can shift the tone of a track without changing the tempo or vice versa. I tend to use Sony Soundforge for this, but I’m sure that professional musicians probably use something far superior for that.

For instance, this is how I’ve done it in the past. I got a vocal track and started to create a new music track for it. As I started to complete the track, I realized that it was more sluggish than I would like. So I then went to Sony Soundforge, fed in the vocal track and told the program to increase the tempo to 125 bpm instead of the original 112 bpm. It takes a couple of seconds, but when it’s done, I’ve got the same vocal track in the same key, just faster. I then go back to my remixing program, replace the vocal files with the new faster version, change the tempo of the music to 125 bpm and I’ve got a faster song.

On Soundforge you tend to lose some sound quality on the original tracks when you mess with the tempo or pitch, but when it’s buried under music it’s less noticeable.

If you want a great example of what’s possible with sound mixing programs now, see Mark Vidler’s mashups. http://www.gohomeproductions.co.uk/

A remix is generally using a lot of the same instrumentation, the same basic hooks, but changes some major aspects of it. There has to be something that makes it noticeably the same song.