One time I played at a competition (Muchty, I think) I was told I wasn't ALLOWED to introduce my tune set.

If I remember right, I was doing a set of tunes that had been turned into songs by Hamish Henderson, and it seemed to me that the judges and the audience needed fair warning that they were going to get the Hamished versions, not the originals they might have expected in an instrumental competition - but I was stopped before I could say that. Weird.