Claque
Very often a singer would have to pay some money to the claque so that they would applaud him (or her). If the singer did not pay, the claque would hiss and boo. This was, of course, a nasty form of blackmail. In the early 20th century, when the world-famous tenor Enrico Caruso refused to pay the claque in Naples a bribe, they hissed during his singing of the great aria Una furtiva lagrima.