Why is rhythm important even in music sometimes called rhythmless?

The term "rhythmless" is considered inaccurate in the context of musical composition, as rhythm is the indispensable element of all music. Because music is a temporal art, it is defined by its existence in time; therefore, rhythm—described as an "order of movement"—is inherently present in every musical work.12

Music often labeled as "rhythmless," such as medieval plainchant, is characterized by a lack of metrical organization or uniform tone lengths. However, this absence of a strict, recurring beat does not mean the music lacks rhythm. Instead, the relative presence or lack of rhythmic differentiation serves as a stylistic determinant. In such cases, rhythm functions as an "inspired organic order of movement" that communicates intelligibly to the senses, even without the mathematically definable structures found in metrical music. Ultimately, rhythm is the process of music in time, and it remains essential because it provides the necessary direction and structural cohesion that allows music to exist as a coherent experience.231