jwilzewske: pomerium

Showing posts with label pomerium. Show all posts

Friday, December 15, 2006

Undeutlicheit: Acoustic Surprise in Extemporaneous Performance

DSM: Pomerium performed in The Cathedral of the Immaculate Conception in Kansas City last night. That cathedral sanctuary is beautiful but cavernous—a rectangular shape about 40 meters long, by 20 meters wide, by 20 meters high, with a horizontal-half-cylinder plaster ceiling. It’s a cruciform building plan with a nave crossed by a stubby transept, and the stone altar is in the center of the large nave, raised several steps up from the main floor. The members of Pomerium assembled themselves on those steps in front of the altar. The audience in their winter-time clothing filled the pews in the long part of the nave, so there was an acoustically absorptive-dissipative effect over there. And the upper part of the nave, beyond the transept, was empty pews all the way to the apse—a highly echoic effect in that direction.

CMT: Yes, I was there. Several times during the performance it seemed to me that Alexander Blachly, the director, was re-gauging the reverberation in the cathedral—making adjustments in his direction for attacks, releases, dynamics, and so on, based on his evolving impressions of the acoustics and how the acoustics of the sanctuary was affecting the sound of the various parts and registers. Despite Pomerium having performed in venues like this since the group’s founding in 1972, he and the singers seemed last night to be genuinely and continuously ‘surprised’ by the characteristics of this particular cathedral. I could only imagine that he was wishing he’d had a chance to more extensively check the acoustic properties of the church in advance of the performance!

DSM: Well, there’s checking and then there’s checking. Only a standing ensemble who routinely performs in a familiar, consistent venue really has a chance to truly know and adapt to the strengths and limitations of that venue. What could you do, besides a rehearse in the room? A well-known and basic method for characterizing the acoustical characteristics of a room is to measure the response at a particular microphone position to a brief source of energy, such as a “blank” pistol shot (not usually done in churches) or a hand clap. The use of a deterministic signal (e.g., long-length sequence, sine-wave sweep) is also possible. From the perspective of room acoustic quality, the result usually involves visual inspection of a graphic display of the “room impulse response”, that is, the root-mean-square pressure of the real part of the analyzed signal, measured in decibels as a function of time. A similar sort of graphic can be obtained from a modeling program that uses ray tracing or other techniques for predicting, rather than measuring, the room impulse response. This information can be used for both analyzing the acoustics of a real room or for simulation of the acoustics of a virtual room. You wouldn’t find regular musicians doing that sort of thing—especially not on the budgets that typify chamber music and early music. But, if you had your ‘druthers’, that’s the sort of thing that you’d like to do…

CMT: And then post-analysis of the reflection amplitudes relative to the level of the direct sound would determine their significance in terms of audibility and clarity. Early reflections are well-known to be potentially detrimental to timbre reproduction, speech intelligibility, and the formation of spatial images in a sound field.

DSM: You remember in Bang&Olufsen’s old ‘Archimedes’ project, the hypothesis to be tested in the project was that the interaction between the sound source and the room has an influence on the perceived sound quality (timbre)? The hypothesis was verified in a Round Robin Test (RRT) in different listening rooms, which included as variables the room, the directivity of the source, and position of the sound source in the room. The results showed that the room has a significant influence on 1) the reproduction of timbre in all positions for all sources, 2) timbre differences between different sources in the same position, and 3) timbre differences between the same source in different positions.

CMT: Yes, in the B&O RRT, the purpose of the project was to examine the influence of individual reflections on the timbre or localization of sound reproduced by a single source in a listening room. The setup simulated the physics—mathematically speaking, the ‘transfer function’—of individual reflections in addition to the attenuation due to distance. The simulated transfer functions included the frequency response of the off-axis angle of the reflection path from the original loudspeaker and the frequency dependent attenuation of the reflection from the simulated room surfaces. The first-order floor reflection contributes on an individual basis to the timbre of the sound source for a sound field that has many harmonics—a noise signal, say; or an ensemble with lots of polyphony, many players and parts. An increase in the level of the first-order reflections either from the floor, the left-hand wall or the wall behind the listener will influence the timbre of later-arriving reflections and noise.

DSM: The threshold of detection for timbre and a noise signal seemed in that study to be determined by the spectral changes in the frequency range 500 Hz —2 kHz The threshold of detection for localization of the later reflections and noise seems to be determined by the spectral changes in a frequency region above 2 kHz.

CMT: I was thinking about that last night. Despite the fact that I sat in Row #2 not 10 meters from the center of Pomerium members, the soprano and alto and countertenor voices and their reflections were far more clearly audible than the bass. And as the singers changed positions with almost every piece, we had an unusual—Unintended!—opportunity to observe the effects on the different parts and registers. The baritones seemed to be immune to positional effects. The tenors were, at various points, the hapless victims.

DSM: You, pitying tenors? Hah! Although it’s common to characterize hall acoustics in terms of a single number—reverberation time—there’s much more detail that affects how listeners perceive the music, and how the performers and the director interact with each other. In a large room, listeners hear the direct sound of the performers, followed by many variably-delayed reflections of the sound—bouncing off many different surfaces that are at different distances from the performers and different distances from the listener. Early-arriving reflections within about 50 msec after the direct sound are especially important—our brain tends to associate them with the direct sound, and we perceive it as louder rather than being diverted by a “different” sound. (This was published by Haas in 1951, but it was something others had known about for almost 100 years before that.) Later-arriving reflected sounds are not processed by the brain in this way, and cause one sound (note) to mask or interfere with the next. I think this is partly what was going on among the members of Pomerium last night.

CMT: Lochner and Burger developed the concept of “useful-to-detrimental” sound ratios, where ‘useful’ is the sum of the intensities of direct and early-reflected sounds and ‘detrimental’ is the sum of the late-arriving sounds plus background noise. Obviously, the judgments ‘useful’ and ‘detrimental’ are too simple for music—the ratios were developed initially for studying intelligibility of speech, not music. But other not-so-simple but more appropriate measures have been proposed—ones that take into account some of the values in musical aesthetics. Gade’s ST1 metric, for example. That one is basically a metric that quantifies a musician’s ability to hear himself/herself and maintain a graceful balance of his/her own instrument or voice with that of the others.

DSM: You could see in the singers’ eyes the fact that they were exploring that cave, that sanctuary—discovering as they sang their way through it just what acoustical support the chamber was giving (or not giving) to their performance. The subjective impression you could read in their eyes was “…I need to have some sensation that my voice has filled this chamber … I am trying to find out when my voice has reached the last row of seats … I want to feel that my voice has slapped back to the altar here.”

CMT: Yes, really, what impressed me last night—apart from the beauty that Pomerium achieved in their singing—was their esprit de corps in adapting to the idiosyncratic acoustic properties of the cathedral. The uncertainty of the acoustics—in a chamber where the performers didn’t have the luxury of being able to rehearse and calibrate themselves to the reverb or other effects in advance, and therefore have to discover and adjust their performance on-the-fly—this didn’t daunt them. In fact, it’s a type of “inadvertent improvisation” that’s typical of early-music performances in cathedrals or other historical venues. Some performers are annoyed by it, I know. But, facing the challenges head-on, Pomerium seemed to find the “discovery” aspects of extemporizing their performance in that cavernous chamber illuminating. Sort of like camaraderie in rock-climbing or other “extreme sports”. When successful, this does tend to bring the aesthetic-athletic feeling of “winning”. Maybe early music in period-appropriate settings is inherently ‘extreme’ chamber music!

DSM: So is it the shape of the chamber that matters most? Is it the sheer volume or size of it that matters? Is it the position of the sound source and the position of the listener that dominate these things? Are some particular registers of the instruments or voices affected more than others, based on the geometry of the room and some resonances or harmonics that the room supports? Is it the “people density”—the room’s volume in cubic-meters-per-person?

CMT: All of those things, in various complicated ways. You might want to have a look at one or more of these recent books on acoustical physics and architectural acoustics.

Thursday, December 14, 2006

Pomerium: Carnatic Christmas?

CMT: Pomerium’s performance of Gregorian chant and monophonic devotional songs (cantiones) for the Christmas season is a wonderful “gallery”—it illustrates the progression from monophonic to polyphonic expressions by Medieval and Renaissance composers. It’s captivating to listen to—especially during the holiday season. More than this, it inspires my interest in history. To get to the polyphony produced in the Renaissance, you must roam through the church prior to the 17th-Century—monophonic chant. That’s part of what Pomerium’s performances and recordings evoke for me.

DSM: Are you thinking of these as independent works of art, or are you thinking of the earlier pieces as “origins” for the polyphonic elaborations of already well-known melodies and words?

CMT: The Renaissance elaborations are—who could deny it?—a progression. Even more so, given the cultural practices that motivated these pieces’ existence. You could say it’s similar to progress in Renaissance painting in these same centuries, as painting moved from stylized two-dimensional figures to three-dimensional representations. So here is Pomerium performing Renaissance pieces composed when it was widely accepted that music could be and should be representational—could represent specific ideas and emotional states. And here is Pomerium performing medieval chants and earlier Renaissance elaborations with sparse, non-representational, serial, rhythmic spell-casting.

DSM: The plainchant expert, Kenneth Levy, spent some of his career investigating the shift from an oral tradition to the written versions. In his book, Gregorian Chant and the Carolingians, Levy looked specifically at stages of the evolution and dissemination of plainchant. How many traditions of chant were there prior to the tenth century? Is one version more authentic than others? Levy discusses these topics, the origin of Latin neumes, the shifting relationships between memory and early notations—not only as a musicologist but as an historian. If Pomerium inspires the historian in you, you should get a copy of Levy’s cool book.

CMT: Gregorian Chant—I think of this music as intrinsically religious, don’t you? Admittedly, I grew up in the U.S., and so all of my reflexes are conditioned by western social patterns. But when I hear Gregorian Chant, all my associations for monks and monasteries in the middle ages are activated. It’s impossible for me to hear this music any other way. For me, ignoring the extramusical associations would interfere with the meaning.

DSM: I’m not sure about that. We can listen to that kind of music as abstract, and the music may be better without “the program”. Monteverdi, when he started composing in the “seconda prattica” style, said that music must serve to the words, not the other way around. So, to him, music must represent the feelings, movements and ideas implied by the lyrics.

CMT: Well, I can hardly but think that the monks themselves regarded Gregorian Chant as part of their devotions, not as a symbol that I as a cultural outsider take it to be. The old monks certainly didn’t know anything about the 20th century discipline of semiotics or linguistics.

DSM: Maybe so for the ancient monks, but the contemporary ones know very well about plainchant semiology! And those of us non-monks who like chant and who’ve read a little philosophy of language know about semiology—know what’s semiotically happening when we’re engaging with this music. As you know, the tradition of Gregorian chant declined by the 13th century and had almost disappeared when it was reconstructed in the 19th century. The church musicologists then valorized the oldest collections of chants. But it happens that those are written in neume signs, and not on the four or five lines of latter staff. So it was necessary to interpret and trans-literate the medieval neumes into the modern staff. And for this a whole science was constructed by Don Cardine, a late Benedictine expert in Gregorian chant. This reconstruction of Gregorian chant is quite a semiotic work of interpretation. Hermeneutics gone wild! There’s actually very little certainty about what notes the neumes actually represent. Neumes are glyphs, ideograms, diagrams, iconic signs—of the rhythmic flow of the Latin texts than melodic lines, but with the help of rules then-current in the prosodic theory of modal music, the monks were able to guess what the music should be, and that’s what we hear today in early music performances. Besides, if we think about the ancient work of writing music with neumes, devising those glyphs and so on, it’s clearly the practice of a musical semiotics.

CMT: I suppose that saying that Gregorian Chant signifies religion, or that western music is a symbol for western culture, is only true for people outside the system. For people inside the system, the signification is superfluous—it doesn’t have any point.

DSM: Well, I don't think so. The indexical reference of the kind you mention is important in India. Indian classical musicians are very conscious of their music and others’ music.

CMT: Yes—Indian carnatic music! A particular Raga may intrinsically mean “evening” to someone inside the relevant cultural system, but not at all to someone outside it. Meaning depends on who you are, and what your cultural background is. Semiotics experts are well aware of this relativity.

DSM: Yes, but this isn’t just a matter of “relativity”. Musical meaning arises in multifactorial networks of sound and action, inserted in the context of culture and expression. What makes sense when we learn that Raga Megh represents the rainy season in India is not that it’s some arbitrary symbol, but rather that that raga evolved in such a way as signifying a conflation of feeling, practices and ideas related to the experience of the monsoons in India—very important in Indian culture and literature. Rains in India are the end of dry Summer; rains means that planting will be possible; rains mean a time for leisure and celebrating. In the rainy season, there several popular festivals in India. Raga Megh implies all that.

CMT: All these ideas are accessible to the western listener as soon as she or he understands and has the aesthetic sensitivity to appreciate the music and the several layers of meaning. To learn and appreciate raga music in this way isn’t different than learning about Norse myths and the cultural motivations related to Wagner’s music. You agree that studying Wagner is not exceptional if you want to listen to his music, the same with Indian music, Gregorian chant, or any other musical culture?

DSM: Maybe the paradoxes also arise from trying to pretend that 20th century semiotics is part of traditional Indian culture. Or not understanding what someone from another culture really means?

CMT: Well, the negative syntax I find in the work of some modernist composers is emblematic of post-modern deconstruction. To me, 12-tone compositions read like Jacques Lacan, Julia Kristeva, Jacques Derrida. And, surprisingly, some of those same feelings are evoked by medieval chant. The intertextuality of the words and the notes. How strange that we would both see parallels in Indian carnatic classical music and Gregorian Chant!