To start with it is important to understand the difference between tala and laya. The tala is a structure based on a predetermined number of beats and is cyclic in nature. Laya implies the tempo or the speed at which the tala is executed.
Talas used in sitar recital are usually ‘trital’ (16 beats), ‘ektal’ (12 beats), ‘Jhap tal (10 beats), Roopak (7 beats) etc. Lighter pieces (usually) called ‘dhuns’ are also played in talas like Keherva, Dadra, etc.
The concept of Laya has been developed into specific categories on the basis of ratios of 1:2, 1:3, 1:4 and so on. The concept implies doubling, trippling and quadrupling the execution as compared to the original tempo. These categories are known as ‘Jatis’ having the nomenclature of Dugun (Dwigun) and Tigun (Tishra Jati) and Chaugun (Chatushra Jati), etc.