When a pianist speaks about his or her "repertoire", it means
all the pieces that he can play. Most famous musicians have a
wide repertoire (they can play a lot of pieces). The "piano
repertoire" means all music written for the piano. The violin
has a much larger solo repertoire than the viola. That means
that much more solo music has been written for the violin than
for the viola. A theatre company may have a "repertoire". That
means all the plays that they regularly perform. Sometimes
theatre companies are called "repertory theatres" because they
have a particular list of plays that they perform.