Hat Band 1 was myself, figmo, tsukara, and nicachick007 doing Come Ye Knights, by Sheila Willis (1/3 of Technical Difficulties, which recorded it) -- it's the source song for Dairy Queen (by Barbara Higgins). What was really cool was that neither tsukara nor nicachick007 knew the song before the weekend; we had issues meeting at any time before the open filk, and nobody was really pushing a song, so I suggested Come Ye Knights because I'd been thinking of performing it anyway after Stephen Joel mentioned that nobody does it any more at his presentation, and it dawned on me that if I was going to do it, and had a band, I might as well, you know, do it -right-. So I transcribed the lyrics from the music (I happened to have both TD tapes on my media player), figmo and I, who actually knew the tune, worked out harmonies (well, did enough rehearsal work to work out harmonies that didn't collide much with one another), and traded ideas until we had something workable, while tsukara and nicachick007? Learned the tune, from scratch, listening to it multiple times when they -could- have been, you know, sleeping or whatever. Doing things acapella as basically a group decision -- we started out thinking we could add guitar, maybe drums...but really...why? And the result? SO MUCH FUN. I should have been all autocratic and stuff and given us a name on stage, though. Probably the Time Knights or something silly like that.
[edit: replaced "I have no idea who these people were" with tsukara and nicachick007, since that ain't true no more]