I love Robert Plant - he changes his vocal style frequently between and within songs.
The guy in AC/DC - he's definitely doing something different with his voice.
I realize word pronunciation has something to do with it, but Paul Simon (very 'soft' voice) vs. Bob Dylan (in say, the Boxer - one of my favorites of all time), James Taylor, Neil Diamond (don't throw tomatoes

, Neil Young. I feel like I can 'imitate' some of the way they're using their voice; of course, it doesn't sound nearly as good, but when I 'imitate' these guys - are there any words to describe what I'm doing with my voice ?
And regarding 'pronunciation' - isn't that almost similar to the 'ornamentation' discussion we had on instruments ? One would think we can apply the similar ideas to dressing up our instrumental electric/synth sounds with effects to dressing up our voices. Or not ?