Rhythm is an essential attribute of music. Melodies have some natural points of accent or stress which occur at regular intervals of time and make people tap their feet or clap the hands. The inherent rhythm of a piece of music can be felt even if their is no percussion instrument but percussion instruments enhance the effect of rhythm. In Carnatic Music rhythm is based on a scheme of Thaalams or rhythmic cycles. The term 'Laya' denotes the rhythmic aspect of Carnatic Music. At concert level rhythm is invariably provided by one or more percussion instruments like the Mridhangam or Ghatam. These instruments can also provide independent rhythmic movements (called 'Thani Aavarthanam').
Compositions are set to definite rhythmic patterns identified by the thaalam name. The time unit of thaalam is known as Aksharam. The total number of Aksharams in a cycle and the points of accent or stress distinguish one thaalam from another. There is no absolute time unit prescribed and the tempo of a composition can be altered according to the singer's needs but once chosen, the time unit has to be maintained throughout the composition. A cycle of thaalam is known as. 'Aavartham'
Except in the case of Naadhaswaram the Raaga 'Aalaapana' or extempore elaboration of a 'raagam' is not accompanied by a rhythmic instrument .