beat

The beat or pulse in a piece of music is the regular rhythmic pattern of the music. Each bar (AKA: measure) should start with a strong beat and each bar should end with a weak beat. These may be known as the down-beat (strong, at the beginning of a bar) and the up-beat (weak, at the end of a bar). Up and down describe the gestures of a conductor, whose preparatory up-beat is of even greater importance to players than his down-beat.