>I now know that the expression seems odd in Switzerland thanks to WSIEBER, but how about in the rest of the world? Is it idiomatic to the USA in this sense?

It is common enough here in the UK in the same situations that have already been discueed.

I have always planned to go to a "Messiah from Scratch" where people just turn up, are provided with words and music and sing Handel's Messiah with no previous rehearsal, (ear plugs not always necessary).