Separate the Background Music from the Song?

Your best bet is to look for a karaoke version of your song. Removing vocals from a mix is like removing the eggs from a cake after it's been baked. Somewhere in a studio there is a master which has the vocals on their own track. Removing them is as easy as turning the volume down on that track. The released version only has 2 tracks which everything has been mixed together on...the musical version of a baked cake.

There are plug-ins and programs that claim to be 'vocal removers' but none of them do a satisfactory job. They play with the EQ and try to subtract frequencies in the vocal range.....problem here is that some of the instruments are in the same range. Since vocals are usually mixed 'center' another strategy is to analyze the left and right channels and subtract everything they have in common.....same problem: it's surgery with a meat cleaver.

I have used Adobe Audition to minimize vocals...it sometimes works ok, but the music can sound like it's underwater and there are still faint vocals. What song are you trying to strip? I could give it a shot with my software.