I'm glad I'm not the only one. I've had very similar ones to Will and Mark Ross, and I've recognized them as a variation on the old 'naked on a bus' or 'missed the exam' anxiety dreams.

Mine always start with things looking really good. There's a packed house, simmering with excitement at my forthcoming performance, then something or other starts to go awry and the whole thing unravels hideously. Quite often it's a lost instrument (usually the concertina), or the PA doesn't work, or I can't find my way to the stage - like that scene in Spinal Tap. Quite often the supportive crowd then turns ugly, and begins jeering or slow handclapping (only in the dreams, I should stress).