Hindustani Classical Music is composed of notes and certain combinations of these notes leads to formation of raga. Raga is a sequential collection of swaras. Raga is divided into two systems Hindustani (North Indian) music, Carnatic (South Indian) music. Artists use their own tonic frequency for singing raga. Each raga is performed in certain time in a day and represent unique emotion. Automatic identification of raga has applications in areas like recommendation system, tagging system, real time detection of raga. In this paper, we have analyzed past works in identification of raga and challenges associated with it.