Claque
In the 19th century there was very often a claque at performances of an opera. Someone who liked one of the singers and wanted them to have lots of applause would pay a group of people to sit near the back of the opera house and to clap and shout enthusiastically whenever that singer had finished a song. This would encourage the rest of the audience to clap loudly too. Sometimes the claque would be paid to do the opposite: they would be told to hiss and boo when the singer had sung.