It is important for a raga to be interesting and melodious. When the raga rules are relaxed in vocal and instrumental music and a composer takes the liberty to do so, it is known as Aavirbhava and Tirobhava. The process by which one flows back easily and effortlessly to the moola (original) raga is called Aavirbhava – Tirobhava. This is never used in Khayal gaayan. It can be used in Upashastriya gaayan and Lalit gaayan.
Eg. Sa Re Ga Ma ni Dha ni Ḿa Pa : Hamir raga
Ḿa Pa Dha Pa Ma : Kedar raga
Pa Ga Ma ni Dha Pa , Ga Ma Re Sa : from Hamir raga to Kedar raga and then back to Hamir raga.
In this composition, Hamir raga swars are sung first. Then we did Tirobhava in Kedar raga swars and then by Aavirbhava we went back to the original Hamir raga.