BlueRaja's summary of helpful comments below the question:
Music and vocals are usually combined in the studio before the song is released. If vocals and music are on the same combined track, there will be no reliable way to separate them, since removing “vocal sounds” of a certain frequency will also remove “instrumental sounds” that appear at the same frequency. (read: sounds sound, and “vocals” are a kind of “instrument”.)
However, if vocals and music are encoded on separate tracks, it will be possible to separate them.
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