How can I sample vocals from an existing song?
sample or extract?
Extracting works, if the song is pure (meaning you don’t have an MP3 compressed in joint stereo which makes the filtering process impossible) , there is software that can filter out vocals or extract vocals comparing left and right channels and remove equally shared frequencies (as it is with vocals).
But that’s just a rough cut, you also have to filter out other frequencies which is quite hard to do.
Various wave editors like Audition can doe this.
Wavosaur has a vocal extractor, which by the way is called “vocal remover”… seriously. Don’t expect miracles. It very much dependant on the mix. I’ve not seen this in Audacity, only the opposit, Kareoke, removing the vocals keeping the instruments.
Contact the author of the song and ask for the original tracks.
…in theory, if you have the instrumental version you can invert the phase then mix it with the full version.
The result should be the vocal track.