Bihag is a Hindustani classical raga.
Writing about the musical theory of Indian classical music is fraught with complications. First of all, there have been no set, formal methods of written notation. Indian music is an aural tradition, and therefore writing is not an essential part of attaining jñāna (knowledge).
Bihag uses both shuddha Ma (ma) and teevra Ma (Ma).
Both R and D are never used in ascent, but always on the way down. That is,
or
Related ragas: Maru Bihag, Bihagra.
Bihag is usually assigned to the Thaat Bilaval, but if Teevra Madhyam is given more importance, Bihag seems to be more akin to Kalyan Thaat.
Behavior refers to practical aspects of the music. It is complicated to talk about this for Hindustani music since many of the concepts are fluid, changing, or archaic. The following information cannot be accurate, but it can attempt to reflect how the music existed.
Bihag is played in the night (second quarter of night). The mood of the raag is celebratory as well as romantic, making it a common raag sung especially on occasions of marriage.
Certain ragas have seasonal associations.
The real origin can be traced back to pure classical raagas widely prevalent in the 16th century, and in many folk songs in the Vaishnava period (14th-18th century). It is used in many songs of Tagore and in various Bengali and north Indian compositions.
A portion of the alap of raga Bihag may be seen in a scene from Satyajit Ray's 1958 film Jalsaghar, played by the surbahar player Wahid Khan, from 29:50 to 31:58. Dil cheez kya hai from Umrao Jaan contains elements of Bihag.