Generally, audiences clap at the end of a complete piece. For instance, a symphony has 4 movements, and it's customary to wait until the end of the entire symphony to clap. This tradition helps maintain the musical flow and atmosphere. However, don't worry if you clap at the wrong time; your enthusiasm is appreciated! It's also traditional to clap for the orchestra, concertmaster, conductor, and any soloists as they enter the stage.