Rhythm is the positioning of sounds in time, or, alternatively, the pattern of durations and accents or stresses given to a series of notes. Whereas paintings and sculptures are compositions in two- and three-dimensional space, music is dependent upon time, and thus rhythm is essential to it. In most Western music, rhythm and pitch operate together to create melody, with the former determining the length of the notes (and any spaces between them) and the latter determining how high or low they go. Music can exist without melody, such as in the drumbeats of some tribal and contemporary works, but melody, timbre, harmony and counterpoint cannot effectively exist without rhythm.
A beat is the division of musical time into equal units, whereas rhythm is variable. Tempo is the speed at which these beats occur. Beats and rhythm are a fundamental, inherent aspect of the human body, such as heartbeats, breathing, blinking, and sleep-wake cycles, and indeed of all of nature, and thus there is a natural affinity of humans for the artificial beats and rhythms in music.