Can't tell a pokok from a kecak?

Until these two books appeared, the literature in English on Balinese music was dominated by Colin McPhee's Music in Bali , going back to the 1930s. While he covered most of the genres found on this extraordinarily vibrant and creative island only the size of Yorkshire, these books focus on one tradition each, so there is still scope for a comprehensive updating of McPhee's pioneering work, in which the kebyar chapter is fairly short, and beleganjur is not mentioned by name but only in references to its predecessor, bebonangan .

Kebyar , covered by Michael Tenzer, is the dominant style of recent Balinese gamelan music. The word which suggests a bursting forth perfectly describes the exuberance and unexpected twists of the music. Changes of texture - and the abruptness of the changes - are a remarkable feature, giving it a highly dramatic quality and distinguishing it from other Balinese gamelan music (and distancing it beyond view from Javanese gamelan music).

Beleganjur , the subject of Michael Bakan's book, is quite another matter, and there are reasons for not even considering it a self-sufficient music. Beleganjur means "marching warriors", referring to the origins of the ensemble one carried into battle to frighten the enemy. The gamelan beleganjur is now used for processions around the village and to accompany the dead to the cremation ground. There is still an element of intimidation in the music, which can be quite deafening, since the rituals necessitate warding off evil spirits. The ensemble comprises small and large knobbed gongs, cymbals and drums. The small gongs are carried, one per player, in one hand and beaten with a mallet held in the other hand. The larger gongs are hung from poles. Each pole is supported on the shoulders of two participants, the rear one also being responsible for striking the gong.

Given that the music of the gongs is based on one note per player (a restriction that does not apply to kebyar ), melodic interest is generated by interlocking rhythms ( kotekan ), that most typically Balinese of musical devices and something that obviously relates beleganjur to at least the upper stratum of the kebyar polyphony. Beleganjur music sounds like the famous kecak ("monkey chorus") translated to an instrumental ensemble, and Bakan explores this obvious connection.

Both books examine music primarily from the past 20 or 30 years, exemplifying the changes in Balinese music during the 20th century, every bit as dramatic as those in western music. Since 1986, there has been quite a craze for beleganjur , comparable to the excitement when kebyar burst on to the scene 70 years previously. Tenzer's exhaustive study gives several useful examples of how the older styles have fed into kebyar , especially the rapid interlocking figurations ( kotekan ) over a basic melody ( pokok ). Drumming, a crucial factor in the control and direction of any gamelan music, is accorded a chapter. Improvisation, something that is not suited to such precise ensemble music, plays a part in drumming, which is all the more impressive when done by the two drummers in interlocking patterns.

Both authors are American composers, performers and ethnomusicologists. Bakan is also a professional percussionist, while Tenzer co-founded the highly successful American kebyar group, Sekar Jaya. Both tend to write as much from a composer's as an ethnomusicologist's perspective, with detailed analytical transcriptions in staff notation (far more in Tenzer's case), supported by excellent compact discs. Tenzer's analyses are especially complex, and the reader has at least one mathematical formula to negotiate. The combination of western analytical constructs and Balinese terminology makes the task of following them even more challenging.

Bakan and Tenzer both renegotiate their position vis-à-vis the discipline of ethnomusicology. The books contain what Tenzer calls "an implicit secondary narrative", which is the authors' personal inner relationship to the music. He lays the foundations of the argument by stating that "Balinese gamelan travels well because it says so much in terms that are not irreducibly Balinese, because it succeeds so beautifully even when abstracted from its context". This is one reason why it has made such a big impact on western composers and other musicians. Similarly, Bakan subverts the fundamental conviction of ethnomusicologists that music cannot be understood except within its cultural and social context by proposing a new approach based on the relationship he forged with his Balinese informant, which belonged to "no 'culture' in particular, neither his nor mine".

As ethnomusicology grew away from the comparative musicology of the first few decades of the 20th century, it discouraged subjective responses and comparisons with western music. What leaps out of these books are the authors' unashamed personal experiences: a series of tragi-comical mishaps from Bakan, and for Tenzer, in his penultimate chapter, a relationship in which he postulates a connection between the modern kebyar composition Wilet Mayura (1982) and pieces by Mozart, Lutoslawski and Ives, as well as a couple of jazz examples. Composers such as Debussy, Britten and Reich, with gamelan connections, are thus deliberately avoided, and in fact neither author devotes much space to considering those composers who responded directly to Balinese music. We know that Balinese music influenced many 20th-century composers, and one of the obvious figures, Steve Reich, provides the foreword to Tenzer's book, in which he sets out his stall as a composer in the age of "world music". But Mozart and Ives? This is not a matter of putting the clock back more than half a century to the days of comparative musicology but rather of pursuing the ideal of unearthing musical universals.

As Tenzer admits quite near the end of his monumental work, the task of following it can be daunting. Neither book is an easy read (but then neither was McPhee's). The appeal of each, especially Tenzer's, will be to those already versed in complex musical analysis. The community of Balinists, gamelan players and ethnomusicologists will welcome these studies as the most significant publications on Balinese music in almost half a century, each a leader in its field.

Neil Sorrell is a senior lecturer in music, University of York.