Several years ago Himself and I spent a weekend at Jenolan Caves west of Sydney, Oz, and also visiting was a school band who were there for a training camp. At night we went on a cave tour - it's dark in the caves, so there's no difference if you tour during the day or at night - and one of the music teachers came on our tour. She asked the guide's permission to play her flute in the caves, permission was given, so our group had a beautiful impromptu concert! The cave tour ends at a big open cave called The Devil's Coach House (Old Nick seems to feature in caves, doesn't he?)and our flautist played there, too.

Jenolan Caves