Some Rishis have been advisers to Kings, like Vasishta, no Siddha is associated as an adviser to King. All Siddhas have been Rishis while not all Rishis were Siddhas. The Yoga system by the Siddhas is slightly different from the one By Patanjali in Sanskrit, though Patanjali is from South and a Siddha. Siddhas have developed alternate system of medicine based on hers found in the South, the Rishis , based on the herbs found in the North.
Yet we find references that rishis have composed the Vedas, Sukthas of the Vedas. And we have , for every mantra, Devatha, Adi Devatha, and Rishis. And many women were also involved in the process. Vedas are grasped from Ether by the Realized Souls.
The Vedas were intutively grasped in the for of Sounds by the Seers,Rishis. They can not be really called composers, they have complied what they have intutively learnt. The major families that composed these hymns are the Bharadvajas, Visvamitras, Vasisthas, Vamadevas, Grtsamadas and Atris. Each of these is attributed a Mandala (or Book) in the Rig Veda. These Mandalas are thus referred to as the Kula Mandalas (Family Books).
Tharpana is a sign of remembrance and an expression of Gratitude to the Sages who have enriched our lies by bequeathing to us the mantras. For details of Rishis of India Timeline, please read my post. One of the groups to be remembered are the Kaanda Rishis. Who are the Kaanda Rishis and why are they to be remembered? The Yajurveda is divided into seven parts; called Kaanda(Chapter) Each chapter is ascribed to be the compilation by Rishi, Sage,. They are called Kaanda Rishis.
It is not Athavana Veda as most people pronounce it. Atharveda is not as large as the Rug Veda. There are 10552 verses in Rig Veda and around 5987 verses (varies slightly based on recessions) in Atharva Veda. Thus Atharva Veda is a little more than half the size of Rig Veda. It is three times bigger than Yajur Veda or Sama Veda. From the preliminary analysis of the text, it is revealed that Atharva Veda was centered around the northern Sarasvati region and later became the text of the shamans in the Kuru kingdom which got established to the east of Sarasvati (in Haryana