Ron, the point I was making about orchestras and choruses using sheet music was not that their music is like most of what's done at singarounds and song circles (though their lyrics are sometimes much more simple and less repetitive than some folk songs).   The point was that they are able to interpret the music and play/sing it with exquisite emotion even while using the printed sheet. That not only can be done with other kinds of music but often is -- though that doesn't happen in any type of music when a book is used as a substitute for learning the piece, rehearsing, etc.