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-18thcentury). It is used in many songs of Tagore and in various Bengali and north Indian compositions.
Arohana : ‘Ni Sa Ga ma Pa Ni Sa’
Avarohana : Sa’ Ni (Dha) Pa Ma Pa Ga ma Ga Re Sa
Vadi : The Vadi note is Ga.
Samavadi : The Samavadi note is Ni
Pakad or Chalan
Bihag uses both shuddha Ma (ma) and teevra Ma (Ma). It has the pakad Pa Ma Pa Ga ma Ga.
Both R and D are never used in ascent, but always on the way down. That is, Pa Ni Dha Pa Ma Pa Ga ma Ga Re Sa or Ni Sa Ni Dha Pa Ma Pa Ga ma Ga Re Sa
Organization and relationships
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.
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.
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.
The song ‘Hamare Dil Se Na Jana” from the film ‘Udan Khatola’ is based on raga Bihag. Even the song Tere Sur Aur Mere Geet  from the movie ‘Goonj Uthi Shehnai’ released in 1959 is also based on Raga Bihag where Shehnai Maestro Ustad Bismillah Khan first lent his immortal shehnai-performance in film music.