if by remove layers of a song you mean an mp3 its not going to happen .. its impossible to actually take a layer out, the only way thats possible is if you tracked the song and have the pro tools, logic, etc. file type it was recorded on to which certainly wouldnt contain mp3s =] if you need to simply cut parts to make ringtones or chop a song for a video audacity will be fine .. for a professional video house you'd want to export it as an .aiff at 48k =]