Is applauding for the choir during Mass considered sacrilegious?
I would not say it is sacriligeous, but it is in very bad taste. Liturgical singing is not performance. The faithful should show their appreciation by singing along or participating, not by applauding. Priests should teach the faithful that this is not appropriate. What ends up happening is that no matter how mediocre or downright inferior the music is, the remaining people in church (since most have already left by the end of the song: in itself proof that hardly anyone understands what the music is for) applaud the choir. How sad.