[Charlie_M]

I'm not sure what kind of problem you're facing here but one thing I tried recently and liked for the same purpose is to first figure out which instrument is competing with the vocal (in the same frequency range) and automate the eq on that such that when the vocal is going, the part of the signal that's currently competing with the vocal gets taken down a bit. You could dip the volume of the competing instrument instead and that may work but may be less subtle. Really though I'm assuming a lot here about what's going on in your track. It would be best to post the track (or a clip) in the "reviews" section to demonstrate clearly what the issue is. Words fall short in decribing these things sometimes.

Good luck and congrats on the apparent success of your track.

Charlie