I just saw Greg a couple weeks ago, for about the 5th time. He tends to experiment with (some of) his songs over time, he's not one of those people who sound exactly like their recordings. I'm not a fan of that procedure but hey he's an arteest. Maybe this is where the so-called mumbling slips in, though I've never noticed it myself. I think the sound quality is probably pretty poor on cell phone youtube clips. ;-) If I could sing like anyone it would be like Greg, but I'd have to swallow a couple of 100 gallon barrels to sound like him.