That reminds me, one of the most amazing things I ever heard was Holly Cole at the Showbox. This intimate dinner/jazz club seated only about 100 or so. The show started with no one on stage. No announcer. No introduction. Everyone was chatting when Holly Cole began singing I Am Calling You from off-stage.
Just Holly Cole. No mic. No amp. That place got quiet, FAST!
The song starts out very low and builds. As it does she comes on stage, still unamplified. Wow. String bass and piano join in. Pure acoustic bliss!
For the rest of the night she used a mic. Just too hard on the chops not to, I guess. But I asked around the table at the end of the night, everyone agreed that was the best part and the most exciting thing most of us ever heard.