The title of "music director" or "musical director" is used by many symphony orchestras to designate the primary conductor and artistic leader of the orchestra. The term "music director" is most common for orchestras in the United States. With European orchestras, the titles of "principal conductor" or "chief conductor" are more common, which designate the conductor who directs the majority of a given orchestra's concerts in a season. In musical theatre and opera, the music director is in charge of the overall musical performance, including ensuring that the cast knows the music thoroughly, supervising the musical interpretation of the performers and pit orchestra, and conducting the orchestra.