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STUDY OF THE TIME THEORY OF RAGAS BY ANALYSING SITAR SIGNALS Aditi Mondal, Madhuporna Ganguly, Anirban Patranabis, Kaushik Banerjee, Ranjan Sengupta and Dipak Ghosh Sir C V Raman Centre for Physics and Music, Jadavpur University, Kolkata Hindustani music with its diverse characteristics and uniqueness is really pleasing to hear. There are many features in it which are appreciated by the world’s music connoisseurs and researchers. There are various areas in it which needs thorough investigation. This paper deals with one such area on which very little objective research has been done; the time theory of Hindustani music. The origin and development of Indian music shows how notes were created: from gradually one note to seven natural (suddha) notes and finally five more sharp and flat (vikrit) notes or positions in an octave. In this way, from the combination of notes, different musical genres have been created. Time theory is supposed to be a subsequent concept in Hindustani music. It was probably Pandit Vishnu Narayan Bhatkhande who first elaborately classified all ragas in Asta prahars (subdivision of a day, approximately three hours long). Time theory of ragas is based on some musical parameters. These are: Nature of notes: that is whether notes of a raga are natural (suddha), flat (komal) and or sharp (tivra). Flat Re, Dha notes uses in those ragas of twilight and dusk, the conjuncture of day and night. All natural notes are uses in the ragas of the first two prahars after twilight. During the third and fourth prahar of day or night after the twilight (that is from 12 noon to 6pm and might night to 6am) ragas of flat Ga and Ni are sung or played. Position of notes: in Indian music an octave divided into two sections or angas (tetrachords); from middle Sa to Pa is Purbanga (lower tetrachords) and from Ma to higher octave Sa is Uttaranga (upper tetrachords). Now if the vadi note of a raga is in between Sa and Pa than it is called Purbanga vadi raga or Purbanga raga. Similarly, if the vadi note is in between Ma and higher Sa then it is called Uttaranga vadi raga or Uttaranga raga. Convention is those Purbanga ragas are to be performed between midday and midnight and Uttaranga ragas between midnight to midday. From the position of vadi note the nature of a raga can also be determined. Purbanga ragas are generally calm, grave whereas Uttaranga ragas are agile or inconstant. So, the meend and duration of notes and tempo are also differing from Purbanga raga to Uttaranga ragas. Here we have taken only the aalap (without rhythm part) of eleven ragas belonging to five thaats (basis for the organization and classification of ragas) played by a single artist in Sitar. Two minutes from each signal were chosen where all the phrases were played clearly by the musician. Perceptual tests were performed among thirty expert listeners of music. From the result of this it may be inferred that the essence of the raga remains unaltered irrespective of time of listening. A mornig raga or an evening raga when listen in the afternoon may be felt as morning or evening raga. From the pitch contour of each musical signals, steady states and silence were identified. Total number and durations of such steady states and also silence were measured. From the steady states we have identified the vadi (most used notes in the raga) notes and that is being compared with the standard theory in music grammer (purbanga and uttaranga vadi notes). Beside this other important acoustical features measured from the acoustic spectra are: note density (number of notes per unit time), average duration of steady state, average silence duration, silence to note ratio, meend (transition between notes) duration, meend frequency and frequency vs partial number. It has been observed that the note density is very less and average note duration is comparatively higher in the ragas belongs to midnight and early morning. Ratio of silence duration to note duration is less during ragas belongs to early evening and late morning. Longer silence and meend durations were observed in the ragas of early morning, late evening and midnight. From the long term average spectra (LTAS) of each signal we have identified the frequencies of each partial. It was also observed that the ragas during evening and midnight shows comparatively much higher frequencies per partial number than the ragas in the morning. Anova was done to check the reliability. These features are compared with the results obtained by the perceptual tests performed. This study helps the amateur musicians and researchers to get in depth knowledge of time theory which is well established in the grammar of Hindustani music. This study also helps in making further new compositions beautifully and authentically. A proper knowledge of time theory enhances the music genre of Hindustani classical music.
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