MP3 Karaoke has been designed to turn mp3 files into minus-one songs by removing human vocal from the tracks.
If you're a karaoke fan or just fond of singing along to your favourite songs and have never tested a program like this before, this application may seem great to you; as not every song is available as a karaoke file and with this piece of software you will be able to create as many karaoke files out of your songs as you wish.
The interface of the program is very clear and simple: you press a button with the big green cross, add the file or files you want to convert and there you go: in a pair of seconds you get the resulting file. The thing is you may not be satisfied with it. In my testing some outcoming music files were just fine: the sound quality stayed the same as in the original, the vocal was completely removed and the whole audio file sounded great. But the situation with the next five songs was completely different: the quality was appreciably low and instead of the vocal track there remained some kind of a metallic echo, very unpleasant to ears.
As far as I could figure it out, if a song involves vocal with special sound effects added to it, then it is very likely that the voice won't be eliminated completely and turn into this awful metallic noise. Some synthesizer or computer sounds can be removed as well, especially if they sound louder or higher than the other ones.
Another downside is that the program doesn't let you implement the lyrics and thus you won't be able to create a full-fledged karaoke song. If you're still interested, you can try MP3 Karaoke and decide for yourself whether it's worth using. At least you're not asked to pay for it.