Music Editing Geekery!

Typically filters that do this just isolate the centre channel (that is, anything that is the same in both left and right), and treat that as the vocal track. I've seen filters for Winamp etc. to do it, usually under the name "Karaoke".

You're unlikely to get a good-quality result without specifically obtaining a copy of the separate backing and/or vocal tracks, though.

<!-- s:s --><img src="{SMILIES_PATH}/cats/aggravated.gif" alt="hmm" title="hmm" /><!-- s:s --> Then how do people manage then? Theres loads of songs that have been cut up and put together with different music under the lyrics or putting new lyrics to old tunes. Do they have to recreate the original music from scratch? Is it just a matter of sampling a section of the original instrumental track and looping it? <!-- s:? --><img src="{SMILIES_PATH}/cats/confused.gif" alt="confused" title="confused" /><!-- s:? -->

Probably a combination of the two. Or they might just have access to a Karaoke version or whatever, I'm pretty sure that these things are available from the music companies (I know that a lot of radio shows seem to have access to versions with no vocals).

Doing it automatically is a hard, inaccurate process though.

Yeah. To get it perfectly clean is pretty hard, but a lot of vinyls (and occasional CD singles) give you either an acapella or instrumental version of the song.

If it's instrumental, you can invert it and combine it with the original song, which should produce the exact effect.

Alternatively, search online for an acapella and see if some other kind soul has already done it, and made it available for download.

What song was it?

For the record, I found a [url=http&#58;//forums&#46;somethingawful&#46;com/showthread&#46;php?s=&amp;threadid=2429549:f020d]thread on the SomethingAwful forums[/url:f020d] (&lt;- click) which goes into a little more detail than this thread, but the bottom line is really that it's almost always pretty much impossible. Even taking a difference between an acapella and the full track won't get you the backing music since it will filter out some of the instruments which occupy the same frequency range (although it will work better than many other methods). Edit: From that thread, [url=http&#58;//youtube&#46;com/watch?v=S0BLpoEYx4U:f020d]click here for a YouTube tutorial on using tracks like acapellas to remove vocals or whatever from a song[/url:f020d].