guitar track doesn't play

When you play a song, you can hear song.ogg, but guitar.ogg doesn't play when you hit the right notes, fofix -v gives the following:
(W) Unable to load guitar track: global name 'zeros' is not defined

This is because in the if-statement on line 223 in /usr/share/fofix/src/Audio.py is commented, so Python interprets line 231-233 as part of the Sound class, instead of part of the global space. De-indenting lines 231-233 by two solves the problem.