One of my favorite concert experiences involved Jimmie Spheeris.  He opened 
for The Moody Blues at Madison Square Garden-I think it was the summer of 
'78.  He was by himself with an acoustic-of course, virtually nobody in 
attendance had heard of him, so there was a lot of talking going on.  The 
Garden is a huge venue, so the din started getting pretty loud and annoying, 
especially to Spheeris, who was clearly getting more and more miffed as the 
time went on.  Finally he started changing the lyrics to one of his songs, 
singing something like "yeah, you try playing by yourself in front of 15,000 
f***ing people who don't give a s**t who you are", etc...Some people in the 
crowd became slack-jawed, some laughed, but most kept talking.  Finally, 
after the song was over, Spheeris said "hey, it ain't disco", and everybody 
laughed, and were much quieter for the rest of his set.

I guess sometimes a well-timed line is all it takes.

David