Conducting is the art of directing a musical performance, such as a concert, by way of visible gestures with the hands, arms, face and head. The primary duties of the conductor are to unify performers, set the tempo, execute clear preparations and beats (meter), and to listen critically and shape the sound of the ensemble.The conductor typically stands on a raised podium and he or she may or may not use a baton. Most conductors do not play an instrument when conducting, but in some cases, a conductor may lead an ensemble while playing a keyboard instrument or the violin (see Concertmaster), particularly with Baroque music. Communication is typically non-verbal during a performance (this is typically the case in art music, but in jazz big bands or large pop ensembles, there may be occasional spoken instructions.) However, in rehearsals, frequent interruptions allow the conductor to give verbal directions as to how the music should be played or sung.Conductors act as guides to the orchestras and/or choirs they conduct. They choose the works to be performed and study their scores to which they may make certain adjustments (e.g., regarding tempo, repetitions of sections, and so on), work out their interpretation, and relay their vision to the performers. They may also attend to organizational matters, such as scheduling rehearsals, planning a concert season, hearing auditions, and promoting their ensemble in the media. Orchestras, choirs, concert bands and other sizable musical ensembles such as big bands are usually led by conductors.