A Knowledge Based Signal Processing Approach to Tonic Identification in Indian Classical Music

In this paper, we describe several techniques for detecting tonic pitch value in Indian classical music. In Indian music, the rāga is the basic melodic framework and it is built on the tonic. Tonic detection is therefore fundamental for any melodic analysis in Indian classical music. This work explores detection of tonic by processing the pitch histograms of Indian classic music. Processing of pitch histograms using group delay functions and its ability to amplify certain traits of Indian music in the pitch histogram, is discussed. Three different strategies to detect tonic, namely, the concert method, the template matching and segmented histogram method are proposed. The concert method exploits the fact that the tonic is constant over a piece/concert. template matching method and segmented histogram methods use the properties: (i) the tonic is always present in the background, (ii) some notes are less inflected and dominant, to detect the tonic of individual pieces. All the three methods yield good results for Carnatic music (90− 100% accuracy), while for Hindustani music, the template method works best, provided the vādi samvādi notes for a given piece are known (85%).