Elisabeth Vincentelli, the author of the NYTimes piece I posted earlier today from Dec. 31, 2006 (and Arts & Entertainment Editor for Time Out New York) got back to me and said this:

"I haven't heard of bands doing it in the 60s. Maybe some of the prog bands in the 70s? I believe it really started in effect in the early 90s and fully took off in the 00s."

The other article I posted makes it clear that bands were doing it in the 60s, but who started it "in effect" in the "early" 90s? Someone other than Phish? I'm not going to bother her again.