Which South Indian poet and composer has a school of music where Sooryakantam  is called Chāyāvati ?
Muthuswami Dikshitar Muthuswami Dikshitar (March 24, 1775 – October 21, 1835) was a South Indian poet and composer and is one of the Musical Trinity of Carnatic music. His compositions, of which around 500 are commonly known, are noted for their contemplative nature and for capturing the essence of the raga forms through the vainika (veena) style that emphasises gamakas. They are typically in a slower speed (chowka kala). He is also known by his signature name of Guruguha which is also his mudra (can be found in every one of his songs). His compositions are widely sung and played in classical concerts of Carnatic music.
Rishabhapriya Rishabhapriya is a rāgam in Carnatic music (musical scale of South Indian classical music). It is the 62nd "melakarta" rāgam (parent scale) in the 72 "melakarta" rāgam system of Carnatic music. It is the "prati madhyamam" equivalent of "Charukesi", which is the 26th "melakarta". It is called Ratipriya in Muthuswami Dikshitar school of Carnatic music.