I am trying to extract a drum loop from a soundfile, which has a violin loop mixed in. Earlier in the song I got a clean pass of the violin with by itself. I was wondering how I could change the phase of the violin loop by 180 degrees so that when I mixed it in [+~] with the other sample the violin loops would cancel eachother out. Leaving only the drum loop. Does anyone know how to do this with pd? Or any other programs/plug-ins?