hi,
now for some real help.
if you are using a voice to do this, make sure that it's pitched differently to the music.
then try reversing the phase and eq'ing this voice so that, other than in true stereo, it's still heard. you'll have to fiddle a bit, and compromise but it will work as i've done this myself.
it's better if the music is sustained stuff rather than rhythmic.
try logic's bi-aural plugin. i've used this with very good results.
DR9.