Rhythm: explicit dimensions of time or space divided into intervallic time systems; more generally the subdivision of time into structured groupings.
Rhythm is generally referred to as the horizontal dimension of musical expression, playing a critical syntactical role. Intervals of time between events in musical performance is culturally universal, as no change in the vertical dimension (specifically pitch) can occur without incurring a sense of rhythmic meter.
Rhythm is commonly seen as the “interaction between meter and grouping” (Clarke 496).
As a temporal ordering process, rhythm creates anticipation and predictability. Derivation from what is expected causes emotional and intellectual arousal as the brain attempts to structure contextual meaning around this change.
In “A Perceptual Model of Pulse Salience and Metrical Accent in Musical Rhythms,” Richard Parncutt defines a musical rhythm as “a temporal sequence evoking a sensation of pulse” (453).