Askyourgran, I have to wonder why you go to these events if you don't seem to enjoy the experience instead of wondering what the etiquette is.
Apart from interrupting, I don't believe there is an etiquette to follow. To be frank, I think if a person is worried whether another audience member is tapping their foot or not, if the percussionist has a mohican or if the conductor is dressed in an Iron Man suit, it makes them a snob and therefore their opinions are not worth my consideration.