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.
Pavanadūta Pavanadūta (पवनदूत) or "Wind Messenger" was composed by Dhoyin or Dhoyī, a poet at the court of the Sena king Lakshmana who ruled Gauda, in what is now Bengal, during the latter part of the twelfth century CE. His Pavanadūta is probably the earliest surviving example of the many messenger poems which were written in imitation of the "Meghadūta" or Cloud Messenger by Kālidāsa. It tells the story of Kuvalayavatī, a gandharva maiden from the south who falls in love with King Laksmana when she sees him during his victory tour of the world. She asks the south wind to take her message to the king at his court.