The ratios and proportions which sound patterns displayed soon developed into an order called sruti. Gradually the musical scales were standardised and laws were framed to regulate the practice of singing and instrument playing.
This allowed the evolution of melodies and a system of musical notations (raag) to come into being. In its simplest and most obvious form and meaning, a dance is the physical expression of the emotive content of music.
The pleasure of music is in the listening; the pleasure of dancing is in watching that music take a bodily shape and express its meaning in a visual experience. In the Indian literary tradition there is no dearth of critical writings on the art of dance.
Both, at the level of theory and technique, the texts provide valuable information. But the most important and also fundamental among all these works is Natyashastra. It was composed by Bharat, a sage, and its date is generally believed to fall between the 2nd century B.C. and 2nd century A.D (in all probability around the 1st century A.D.).