Natyashastra is the earliest literature on music and drama written somewhere around 500 BC by Bharata Muni. Comprising 6000 couplets in Sanskrit and spread over thirty-six chapters, Natyashastras focus was on dance and drama, with music as an aid. The title is a combination of two Sanskrit words Natya and Shastra. Natya refers to technique of dance and drama, and shastra refers to science. It is the magnum opus that describes relation between director and audience, structuring a play, acting techniques, costumes and make-up, music and musical instruments to be used, the dimensions of the stage and its decorations with lighting, and size of the hall and seating of audience. Directors and producers of plays mention that its relevance is high even in this date and age.

Chapters 28 to 33 dwell on music vocal and instrumental (melodic and rhythmic) and their deployment in drama/theatre. Thus, we may categorise Bharata Munis description of music as (1) vocal, (2) instrumental, (3) vocal and instrumental, (4) preliminary music (as in before the drama begins or just at commencement of drama, and (5) Dhruva music authored by the director and set to music

Natyashastra classifies instruments as (1) tata stringed, (2) avanadha covered percussion, (3) sushira hollow (flute), and (4) ghana rhythm supports like cymbals. The text has even codified the dimensions of the instruments, the material to be used, treatment of the material before they are deployed, and the artisanship to convert the various parts into a single whole instrument. Artisans involved in handcrafting / making instruments today too follow the broad directions mentioned in Natyashastra.

Bharat Muni stressed on a 22 swara octave. It is said he performed a large public experiment to demonstrate the 22 swaras. While the concept of a raga did not exist and was not named so, jaatis and murchanas made up for this lack of definition. Natyashastra defines these in detail in addition to explaining the organising of swaras as vadi, samvadi, anuvadi and vivadi for the jaatis and murchanas.

Bharata Muni expounded the relationship between performers and audience through rasa-bhava anubhava. He elucidated eight types of rasas and their corresponding bhavas that is emotions. A rasa is an emotional state. Very simply put, it means juice or sap. A rasa is usually the dominant emotional theme through a work of art. It is the delight and pleasure experienced directly from art. Bhava means to become. It is a state of mind whose outcome is a rasa.

Bhava is the emotion felt by the character and communicated to the audience via various dramatizations by the performer, resulting in the audience experiencing the rasa. As per Bharata, bhava by itself is incomplete and carries no meaning without the rasa.

Rasa         Bhava    Emotion

Sringara      Rati        Romance

Hasya       Hasa      Humour

Karuna      Shoka     Compassion

Roudra     Krodha      Anger

Veera        Utsaha    Valour

Bhayanaka Bhaya    Fear

Bibhatsa   Jugupsa    Disgust

Adbhuta    Vismaya      Marvel