In reply to Offwidth:
Institute of Contemporary Arts (ICA) London 2001 or 2002, a time when "arty band playing an instrumental live score in front of film" was coming into vogue.
American space-rock band "Sand" were playing a score to Stalker. Support act was London band Saloon playing a score to La Jetee .
I was only really there for the former, as I was a big fan of Saloon at the time and sort of knew them a bit. I knew what a classic Stalker was but also knew it would be a bit of a long haul, so I wasn't really watching it (I was in and out of the cinema discreetly but mostly drinking in the bar and chatting to Saloon).
ANYWAY
Suddenly a bit of a kerfuffle.....and to cut a long story short, someone had been thrown out of Stalker for sarcastically slow-clapping after the infamous still mirror pool tableau scene :-D