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.
Matrigitikanjalih “Mātrigītikāñjalih” is a well-known Gitikavya in modern Sanskrit literature. Authored by Harekrishna Meher, this kavya comprises twenty-five Sanskrit songs of different topics and tastes experienced in human life. These songs are written in very lucid, simple, sweet and graceful words that are capable of touching the core of the hearts of readers. The titles of the songs indicate their themes. The style of composition bears a unique and special feature. There is no verbosity or stiffness in language. Words are imbued with proper feelings and sentiments. Alliteration, grace of diction, Upama, Rupaka and other figures of speech are contextually found in this kavya. The poet has presented these songs with his original innovated new metres and tuning. The songs are marked by original thinking and novel ideas.