Look closely and you’ll see that some of them do! But in general, they are concentrating deeply, just like outfielders waiting for the fly ball or pitchers winding up to a curve ball. They’re “in the Zone.” After the music is over, you may see them smiling broadly. If it was a concerto, and they liked the soloist’s playing, they won’t just smile–the string players will tap their stands with their bows as a sign of appreciation.