beat, in music, the basic rhythmic unit of a measure, or bar, not to be confused with rhythm as such; nor is the beat necessarily identical with the underlying pulse of a given piece of music, which may extend over more than a single beat. The number and relative positions of accented and unaccented beats furnish the basis of proper metric articulation, with the strongest accent usually falling on the first beat after the bar line. In Western musical notation the number of beats to the measure is indicated by the upper figure of the time signature at the beginning of a musical composition, while the time value of each separate beat (e.g., a quarter or eighth note) is indicated by the lower figure. See also metre; rhythm.