Vocal distortion can be the glue that pulls your vocal tracks together. Just a simple side-chain with the vocals being processed through a distortion plugin or amp head can pull the vocals coward in the mix and at the same time find the right pocket for the vocals in the mix. You may be saying to yourself, "I don't want my vocals all fuzzy and gritty." Not to worry, by side-chaining the effect, you can blend in the dry and wet vocal signals to a level that works best for your mix. The distortion will add just enough color to the vocals so they feel like part of the music and not just ambiguously floating above the music. Slap some EQ on the distortion track to get a brighter or darker tone to your distortion coloring. Just don't go overboard with the vocal effects, unless that is the goal for the track. Happy mixing!