12th International Society for Music Information Retrieval Conference (ISMIR 2011) COMPUTATIONAL APPROACHES FOR THE UNDERSTANDING OF MELODY IN CARNATIC MUSIC Gopala K. Koduri, Marius Miron, Joan Serra` and Xavier Serra Music Technology Group Universitat Pompeu Fabra, Barcelona, Spain [email protected],[email protected],[email protected],[email protected] ABSTRACT The two classical music traditions of the Indian subconti- nent, Hindustani 1 and Carnatic 2 , are among the oldest mu- The classical music traditions of the Indian subcontinent, sic and most unique traditions still alive. There are excellent Hindustani and Carnatic, offer an excellent ground on which musicological and cultural studies about them, they main- to test the limitations of current music information research tain performance practice traditions and they exist within approaches. At the same time, studies based on these music real social contexts. Thus, they are an excellent ground on traditions can shed light on how to solve new and complex which to build new information models and a way to chal- music modeling problems. Both traditions have very dis- lenge the dominant western-centred paradigms. In this arti- tinct characteristics, specially compared with western ones: cle we focus on Carnatic music, the tradition of south-India. they have developed unique instruments, musical forms, per- Carnatic music shares with the Hindustani tradition some formance practices, social uses and context. In this article, basic foundations, such as the basic elements of shruti (the we focus on the Carnatic music tradition of south India, es- relative musical pitch), swara (the musical sound of a sin- pecially on its melodic characteristics. We overview the gle note), raaga (the melodic mode), and taala (the rhythmic theoretical aspects that are relevant for music information pattern). Although improvisation plays an important role, research and discuss the scarce computational approaches Carnatic music is mainly sung through compositions, dif- developed so far. We put emphasis on the limitations of the ferently from Hindustani music where improvisation is fun- current methodologies and we present open issues that have damental. Carnatic music is usually performed by a small not yet been addressed and that we believe are important to ensemble of musicians, consisting of a principal performer be worked on. (usually a vocalist), a melodic accompaniment (usually a violin), a rhythm accompaniment (usually a mridangam), 1. INTRODUCTION and a tambura, which acts as a drone throughout the per- formance. Other typical instruments used in Carnatic per- Though all music traditions share common characteristics, formances may include the ghatam, kanjira, morsing, veena each one can be recognized by particular features that need and flute. to be identified and preserved. The information technolo- gies used for music processing have typically targeted the The computational study of Carnatic music offers a num- western music traditions, and current research is emphasiz- ber of problems that require new research approaches. Its ing this bias even more. However, to develop technologies instruments emphasize sonic characteristics that are quite that can deal with the richness of our world’s music, we particular and not well understood yet. The concepts of need to study and exploit the unique aspects of other mu- raaga and taala are completely different to the western con- sical cultures. By looking at the problems emerging from cepts used to describe melody and rhythm. Carnatic mu- various musical cultures we will not only help those specific sic scores serve a different purpose to those of western mu- cultures, but we will open up our computational methodolo- sic. The tight musical and sonic relationship between the gies, making them much more versatile. In turn, we will singing voice, the other melodic instruments and the percus- help preserve the diversity of our world’s culture [26]. sion accompaniment within a song, requires going beyond the modular approaches commonly used in music informa- tion research (MIR). The special and participatory commu- Permission to make digital or hard copies of all or part of this work for nication established between performers and audience in con- personal or classroom use is granted without fee provided that copies are certs, offers great opportunities to study issues of social cog- not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. 1 http://en.wikipedia.org/wiki/Hindustani classical music c 2011 International Society for Music Information Retrieval. 2 http://en.wikipedia.org/wiki/Carnatic music 263 Poster Session 2 nition. Its devotional aim is fundamental to understand the they are wrongly attributed to Bharata, who used shruti to music. The study of the song lyrics is also essential to under- mean “the interval between two notes such that the differ- stand the rhythmic, melodic and timbre aspects of Carnatic ence between them is perceptible”. Krishnaswamy [13] ar- music. And many more interesting music aspects could be gues that the microtonal intervals observed in Carnatic mu- identified of relevance to music information processing. sic are the perceptual phenomena caused by the gamakaas, In the next section we focus on the melodic aspects of i.e. that these microtonal intervals are what few scholars and Carnatic music, over-viewing the theoretical aspects that are musicians claim as 22 shrutis. However, we believe that relevant for MIR and discussing the scarce computational these claims need to be verified with perceptual and be- approaches that have been presented. In the last section we havioural studies. In our encounters with most musicians, present open issues that have not yet been addressed and that we can only conclude that they are unaware of the usage of we believe are important to be worked on. 22 shrutis in practice. Few musicians who claim they are used, are not ready to demonstrate them in a raaga. In gen- 2. COMPUTATIONAL APPROACHES TO MELODY eral, more empirical, quantitative and large-scale evidence needs to be gathered. Our preliminary research on this line The most fundamental melodic concept in Indian classical shows no support for the usage of 22 shrutis [25]. music is raaga. Matanga is the first known person to define The tuning itself, whether it is just-intonation or equi- what a raaga is [28]: “In the opinion of the wise, that par- tempered, is an issue of debate 5 [12, 25]. Since Indian ticularity of notes and melodic movements, or that distinc- classical music is an orally transmitted tradition, perception tion of melodic sound by which one is delighted, is raaga”. plays a vital role. For instance, tuning seldom involves an Therefore, the raaga is neither a tune nor a scale [18]. It is external tool. And even the tambura, which is used as a a set of rules which can together be called a melodic frame- drone, and thus as a reference for tuning, has a very unsta- work. The notion that a raaga is not just a sequence of notes ble frequency. Hence the analysis of empirical data coupled is important in understanding it and for developing compu- with perceptual studies are important. In [25] we have car- tational models. Also the concept of raga has been chang- ried out an empirical analysis of the stable tunings employed ing with time. Nowadays a given raaga can be described by some Carnatic and Hindustani singers. The results sug- by properties such as: a set of notes (swaras), their progres- gest a clear tendency towards just-intonation in the case of sions (arohana/avarohana), the way they are intonated using Carnatic music while, at the same time, they point out to a various movements (gamakaas), and their relative position, strong influence of equi-tempered tuning in the case of Hin- strength and duration (types of swaras). In order to identify dustani music. raagas computationally, swara intonation, scale, note pro- Fixed tunings are not the whole story. In fact, it is a well gressions and characteristic phrases are used (Secs. 2.1 and accepted notion that a note (swarasthana) is a region rather 2.2). Unexploited properties of a raaga include gamakaas than a point [7,27]. Thus, a fixed, stable tuning for each note and the various roles the swaras play (Sec. 2.3). is not as important as it is in, say, western classical music. In addition, Sa, the tonic, can be any frequency. It depends 2.1 Swaras and shrutis on the comfort of the singer or the choice of the instrument In Indian music, swaras are the seven notes in the scale, de- player. A given note can have several variations in intona- noted by Sa, Ri, Ga, Ma, Pa, Da and Ni 3 [27]. Except for tion depending on the raaga. This variability in intonation the tonic and the fifth, all the other swaras have two varia- arises from vocal articulations or the pulling of instrument tions each, which account for 12 notes in an octave, called strings. Even if two raagas have the same scale, the intona- swarasthanas. There are three kinds of scales that one gener- tion of notes vary significantly. Belle et al [2] have used this ally encounters in Carnatic and Hindustani music theory: a clue to differentiate raagas that share the same scale. They 12-note scale, a 16-note scale and the scale which claims 22 evaluated their system on 10 audio excerpts accounting for shrutis 4 . The 16-note scale is the same as the 12-note scale 2 distinct scale groups (two raagas each). They showed that except that 4 of the 12 notes have two names each, in order the use of swara intonation features improved the accuracies to be backward compatible with an older nomenclature.