Maybe the technique I posted seems a little complex (no one seemed to comment on it) but you can get really creative with it with selective inverted phase cancellation. For instance you can create comb filtering if you want or a specific eq curve (you create the subtraction curve by ear), you can also insert an MS inline plugin and choose to remove a portion of the guitar’s stereo field so the vocal spatial effects replace the guitar spatial effects or do a blend of the mid side for specific cancellation to make the stereo field of the song very interactive.
If anyone tries this, make a channel preset after you set it up. Once you get familiar with it and the flexibility and depth in which you can sculpt, you will want to use it other places. I first came up with this for low bass frequency attenuation so a kick could be really punchy without losing the low-mids of a bass guitar.
You can also use this technique in the opposite, to trigger boost in certain frequencies (I usually go for higher frequencies that are at the edges determining width) so that when the vocal enters, the effects of a pad/synth it excited. You don’t need much. The added sonic information, even though it is coming from a different instrument, will draw attention to the content that brings it out because they are linked to each other when they are present. It is a very cool thing how a mind+ear interpret things.
I tend to be really technical in how I approach things.
Or, just purchase a plug that gets your groove on and let it do it for you. 
Like I said: Million of ways to skin a cat 
