The Natya Shastra (Sanskrit: नाट्य शास्त्र, Nāṭyaśāstra) is an ancient Indian treatise on the performing arts, encompassing theatre, dance and music. It was written during the period between 200 BCE and 200 CE in classical India and is traditionally attributed to the Sage Bharata.
The Natya Shastra is incredibly wide in its scope. While it primarily deals with stagecraft, it has come to influence music, classical Indian dance, and literature as well. It covers stage design, music, dance, makeup, and virtually every other aspect of stagecraft. It is very important to the history of Indian classical music because it is the only text which gives such detail about the music and instruments of the period. Thus, an argument can be made that the Natya Shastra is the foundation of the fine arts in India. The most authoritative commentary on the Natya Shastra is Abhinavabharati by Abhinavagupta.
The text, which now contains 6000 slokas, is attributed to the muni (sage) Bharata and is believed to have been written during the period between 200 BCE and 200 CE. The Natya Shastra is based upon the much older Gandharva Veda (appendix to Sama Veda) which contained 36000 slokas. Unfortunately there are no surviving copies of the Natya Veda. Though many scholars believe most slokas were transmitted only through the oral tradition, there are scholars who believe that it may have been written by various authors at different times.
From Wikipedia Article Natya Shastra