Iannis Xenakis, Bohor (1962)

Xenakis selected a diverse handful of sound sources for Bohor, which reflects the diversity of his influences at the time. The sketches for Bohor verify the two known sound sources already documented, the Laotian mouth organ and various "Oriental" bracelets. More notably, they also reveal two additional sources previously unknown: Byzantine chant and piano. Xenakis recorded sound samples of each of the four materials, and manipulated each by stretching, compressing, or assembling different fragments. The final sound entity is quite remote from the starting materials, but one can at times detect a semblance of an original source. Below is a brief overview of the four materials used in Bohor.


The ancient mouth organ of Laos is known as the khen (or khaen), a polyphonic, free reed instrument. The khen is also found in Vietnam and Thailand, and has inspired the Japanese sh_ and the Chinese sheng. The Western harmonica even owes a debt to the Laotian khen. The instrument has two basic components: open-ended reed pipes and a windchest known as the dao ("gourd"). The khen reeds are usually made of brass or bamboo. The length and number of reed pipes can vary. They are arranged in two parallel rows according to height. The oval-shaped windchest helps to bind the reeds together and is made from the dried shell of a gourd. The instrument is held by cupping each hand around the windchest and positioning it at a slight angle across the face, the lower end resting against the body. Sound is produced both by inhaling and exhaling through a circular opening at the blunt end of the windchest, which generates an unbroken chordal continuum. Finger holes appear just above the windchest where the fingers fall. When covered, the reed sounds. Typically, at least one reed pipe is stopped with the finger or with beeswax to produce a permanent drone bass. A low sustaining pitch is a common underlay to a rhythmic melody. While khen music is based on five modes called lai (each of which is an anhemitonic pentatonic scale), the frequent use of octaves, fourths, and fifths creates sonorities similar to music based on the diatonic scale. The khen is a solo instrument but it often accompanies a singer. This combination can be compared to one of Xenakis's other sources for Bohor, Byzantine chant, which sometimes employs drones to accompany the upper voices and thicken the monophonic texture.

khen sample

sample from track 1


The Bohor sketches have imparted specificity about the kinds of "Oriental" jewelry Xenakis used: Iraqi bracelets and Hindu foot bracelets. Most of the percussive sounds of Bohor are likely derived from the ornate silver bells, beads, and chains of Middle Eastern jewelry, and from the small crotal bells attached to bracelets like the ghungr_, worn on the ankles of dancers in India. While the size of such bells can range from the size of peas to chestnuts, Xenakis converts these sounds into a magnificent clamor equal to the effect of massive chimes. A similar technique of augmentation can be found in the middle section of Diamorphoses (1957-8), where the sound of tiny Greek bells worn by sheep is transformed into piercing percussive sounds. The Iraqi and Hindi jewelry of Bohor were apparently used again in Persepolis (1971), the hour-long polytope work set in Iran. Xenakis had been thinking about the relationship between western and eastern cultures when he started Bohor. His earlier electroacoustic work Orient-Occident (1959-60), for example, was created to accompany an Enrico Fulchignioni film depicting the interaction of European, Asian, and African cultures through a survey of their respective artifacts. The following year, Xenakis traveled to Tokyo for an East-West conference and became acquainted with traditional Japanese music and Noh theatre. Both provoked a strong response from him because of the similarities he heard with classical Greek music. Much as Xenakis relied on Iraqi and Hindu articles for the percussive sounds of Bohor, it seems that the analogy of Bohor to standing inside of a large bell may have been inspired by the large bonsh_ bells of the Japanese Buddhist monasteries. He has also used the example of traditional Asian music to illustrate his own approach to sound, characterized by constantly shifting dynamics and sliding pitches in order to create the effect of a sound that is "alive." When elaborating on the pervasive use of glissandi in his music, Xenakis explains, "For me [a glissando] represents the most usual behavior of a sound, while a sustained note is something special because the slope of the pitch versus time changes is nil. Traditional Asian music, for example, has no constant pitch and the sound is always moving around it." In fact, Xenakis has remarked that the constant drone and its interaction wih the surrounding activity are important aspects of Bohor.


When Xenakis indicates "Byzantine" in his sketches, he was likely to have meant a Byzantine singer (psalte). Almost all surviving Byzantine music is sacred chant set to Greek texts in a monodic and non-metrical style, and includes non-diatonic sonorities such as microtones. Byzantine music has been a notable if not inevitable influence on Xenakis's music. His boarding school years on the Greek island of Spetsai entailed weekly attendance at Sunday services of the Byzantine liturgy. While Xenakis admits he enjoys discovering the indirect ways his personal experiences manifest themselves in his compositional choices, he generally prefers to avoid autobiographical elements in his music in search of a more universal frame of reference. He says, "One has to shed the fetters of the pastÉTonal music is one such tie, serial music another, Indian music, Japanese music, and so on, another, they are all separate worlds, continents or islands, each with its own closed rules. One has to examine what these islands have in common, what mental structure is present deep down in all of them; whether there is a path leading to each and whether itÕs possible to create a higher order." The amalgam of different cultural and historical sources in Bohor is perhaps an instance of this intent. Byzantine chant functioned as the liturgical music for the Greek Orthodox Church during the Byzantine Empire (330-1453) and is still studied and practiced in Greece today. Greek instruments were often used in Byzantine ceremonial music, for which the main instrument was the organ. It is possible that Xenakis's combined use of chant and mouth organ in Bohor is an oblique allusion to Byzantine ceremonial music.


The least information exists on how Xenakis handled the piano in Bohor. He may have used the decay of a pitch, the attack point, plucked and strummed the strings of the pianoÕs interior, or all of the above. It is also conceivable that Xenakis prepared a piano by inserted objects between the strings of the instrument so as to create an array of different timbres.

Very little is written or understood about the ideas behind Bohor, and even Xenakis claims to have forgotten how the piece was created in 1962. For the first time, Xenakis's publisher has kindly made available the composer's own sketches for the work and these formed the basis for the following attempt to clarify the ideas underlying Bohor.

Found among the sketches were these hand-drawn contours:

Each corresponds to one of the four sound sources used to create Bohor, as indicated by Xenakis in shorthand toward the left margin of this slide.

These diverse sources were transformed and assembled into a seamless sound continuum, anchored by a heavy drone derived from the Byzantine chant and Laotian mouth organ, and clothed by percussive sound patterns derived from the prepared piano and bell-trimmed jewelry.
Since no score exists for Bohor, this sketch worked as a guide for analyzing the work. It traces the evolution of the 4 distinct layers, but due to the unconventional nature of this musical notation, it was not clear how they should be interpreted. After running Bohor through a computerized pitch and amplitude tracking algorithm, it was found that the first four contours represented the amplitude for each source, while the bottom graph represented the composite course of pitch for each track.
Computationally, pitch is much harder to determine accurately than amplitude, but even with limited accuracy, it is evident that the goal of creating an effect of being inside a bell is achieved by juxtaposing the tracks so that at almost every moment the entire audible pitch spectrum is filled while amplitude is modulated accordingly.

The plots of the actual amplitude have the same main features as the curves on Xenakis's sketches while they certainly show much more structure in a microscopic sound level. This suggests that the sketches are really a guideline score for the piece describing the overall dynamics of the sound elements.
One possible way for Xenakis to have realized this score with the available technology at the time would have been to start with four continuous tapes of processed sound sources and then mix them following the score as an instruction set for the mixing amplitude and pitch shift of each track.
Another common technique, used for example in Concrete PH, is pasting from a library of prerecorded processed short sound elements, amplifying and transposing until the desired parameters are obtained and then mixing according to the score guideline.

Bohor is an eight track piece in which four distinct tracks are mirrored through pairs of speakers. Though Xenakis strives foremost to arouse the imagination of his listeners, the composer has likened Bohor to the experience of listening to a large bell from its interior, which explains the careful choices in the spatialisation of the speakers. Xenakis apparently expereimented with many different spatialisations, the final version of which is shown on the figure:

Xenakis expressly stated that Bohor "needs space" in order to be heard properly and made careful speaker designations for each realization of Bohor, taking into consideration the dimensions and acoustics of its various performance spaces.

Molding a unique amalgam of sounds in this habitat, Xenakis creates an atmosphere that seems both profoundly sacred and industrial at the same time.

Bohor was called a "huge firecracker," by one of its early critics on account of its remarkable surges of volume. The 23-minute journey through Bohor might be said to be a gradual progress from sound to noise--the last 5 minutes feature an increasing distortion of sound until it steals away into an abrupt silence. While Bohor's magnificent clamor, which contracts and flails about at hefty volumes, may yield an all-too-vivid metaphor of bells ringing in our ears (even after we go home tonight), Bohor is a landmark work, for it invites the audience into the interior of sound, into a realm of close-range listening to which we are not often privy.

(compiled from http://www.music.columbia.edu/masterpieces/notes/xenakis/index.html)