At the Warner theatre in Washington, D.C. in the mid -70's Bonnie Raitt was doing a superb show on acoustic and then a drunken Stephen Stills ambled out, seemingly uninvited and joined in for one or two numbers playing some very sloppy slide guitar and then slithered off and the show then got back on track. The one and only time I saw John Prine, also back in the 70's he was so drunk that he mostly guffawed his way through his short set preceding Steve Goodman (talking about sublime/ridiculous). vl