I was supposed to be playing classical guitar in a quartet performance of the Nutcracker,* along with a cellist, pianist, and... other musician? In real life, I haven't played my guitar in ages and can't really sightread.
In the dream I knew it was a bad idea to be sucked into this performance without having practiced with the group--let alone looked at the music--beforehand, but I hoped maybe it wouldn't be too noticeable. I didn't even have the music, so I had to read off the copy of the woman beside me, who was singing as a member of either the choir or the audience.
Naturally, I was terrible. Weirdly, it didn't bother me as much as it should have.
*Or perhaps the Messiah; it shifted.