rhythm and metre

Two aspects of the organization of time in music. Rhythm is the placement of musical sounds in time. Metre, like poetical metre, is usually a regular pattern of beats and provides the context in which rhythm is understood. In Western notated music, metre is indicated by means of a time signaturein which the lower number specifies the basic unit or subunit of the beat (e.g., 8 usually indicates that eighth-notes are the basic subunit) and the upper number specifies the number of beats in a measureat the beginning of a piece or movement, and by the vertical bar lines that divide the piece into measures.