jwilzewske: neurophysiology

Showing posts with label neurophysiology. Show all posts

Tuesday, January 3, 2012

Guided imagery in music training and performance

I n order to have fast mobility and clarity on left-hand fingers, string players have to train their fingers to have these 3 elements when dropping their left-hand fingers on the fingerboard: speed; strength; and the fast release right after the drop. The 3 elements on the left-hand fingers take training to build up the strength of the muscles and the speed of the reflex of the fast release. Of course, any ‘tool’ that we gain from our technical training is ultimately to be used to create music that would touch listeners. Sometimes when musicians concentrate too much on technical elements, their music tends to be too mechanical, too careful, and lacks emotion. By contrast, when musicians concentrate on being musical, it actually helps the technical things. For example, whenever I feel my fingers stiffen in fast passages, I always find thinking something light and bubbly helps to increase my fingers’ lightness, mobility, and fast articulations. Whenever I try to sustain a long note [and yet try to musically project vitality and suspense, despite the temporary absence of pitch-change or the lack of overt dynamics changes while the note lasts], I remind myself about the struggles and tension of the music. Whenever I try to create smooth bow changes, I often picture a [calligraphy] paint brush changing its direction, instead of which muscle to move first!” — Jackie Lee, Heartland Music Academy, 2012.

I n reply to the previous post, I received the helpful advice above.

A nother CMT reader emailed me to ask whether there was any scientific research literature that establishes the effectiveness of visual or kinesthetic imagery in music teaching, especially for soloists or chamber performers.

T here’s lots of published research on guided imagery in the neurophysiology and physical medicine and rehab literature—and in the lit for research on aging and stroke. Quite a lot in the dance and sports medicine lit. But there are not very many published controlled research studies in music performance/pedagogy lit, so far as I can tell.

I will continue looking; please feel free to add comment below or email me if there is a reference that you like.

M eanwhile, here are some links to work that’s relevant to this.

T he left arm functions, to a large extent, by 'walking' on the fingers. In actual walking, torso balance shifts forward, and it is caught on top of the moving legs. For the cellist's left arm, a similar balance can be felt when the upper arm shifts and must be caught by another finger or the arm will fall over... This ‘walking’ image can be strengthened by imagining that the fingerboard is a staircase... Picturing this helps you feel that your balance is aligned in the Earth's gravity, even though your fingers look angled-back in relation to the surface of the fingerboard.” — Jeffrey Solow, cellist, quoted in Bruser, p. 121.

I n automatic or cyclical movements, actual and motor imagery (MI) durations are similar. When athletes imagine only the dynamic phases of movement or perform MI just before competing, however, the environmental and time constraints lead to underestimating the actual duration [and the benefits of the guided imagery are diminished, despite the speed and ease with which the imagery for brief or cyclical movements is called up]. Conversely, complex attention-demanding movements take longer to image [and so guided imagery for complex movements has impediments to its effectiveness, even if duration over/underestimation does not occur].” — Aymeric Guillot, 2005.

T he bilateral frontal opercular regions [in the brain] are crucial in both preparation for and during music execution and imagining. They may have ‘mirror neuron’ properties that underlie observation or imagining of one’s own performance. The motor areas are differentially activated during the preparation and execution or imagining the sequence.” — Rumyana Kristeva, 2003.

D uring execution of musical sequences in professional musicians, a higher economy of motor areas [in the brain] frees resources for increased connectivity between the finger sequences and auditory as well as somatosensory loops, which may account for the superior musical performance. Professionals also demonstrated more focused activation patterns during imagined musical performance.” — Martin Lotze, 2003.

Tuesday, December 6, 2011

Tallis Scholars’ sound, or why 176 KHz/192 KHz HD sampling for choral chamber music is important

I t is known that energy in the 5-20 KHz range can be perceived even when it is 50 dB or more below the main voice spectrum peak. Also, these upper frequencies are conventionally emphasized in the production of popular vocal music. Yet very few studies of the acoustic content of this range have been made. High fidelity recordings were made of singers sustaining vowels at varying levels of vocal effort. A general characterization of the two highest octaves 5-20 KHz was sought. The prevalence of high-frequency energy, the variation of harmonics signal-to-noise ratio as a function of frequency, and the covariation with overall SPL were all highly variable, but several landmark features were identified... [including] clusters of resonances in the regions 7-10 KHz and 13-16 KHz. Harmonic energy was observed to over 16 KHz in strong female voices.”
— Sten Ternström, KTH Stockholm, 2008.

T he Tallis Scholars’ performance in Kansas City tonight was gorgeous. The concert was performed in the Cathedral of the Immaculate Conception, which has a central altar and a wide chancel such that there are myriad acoustic reflections that arrive at one’s ears from multiple directions. Unlike many performance venues where reflected sound for people seated in most locations is predominantly from one or two general directions, Immaculate Conception has quite high reflective efficiency from many of its interior surfaces.

I f you are seated close to the ensemble—not more than, say, 10 meters away from the sound source—the sound projects exaggerated cues of ‘spatiality’, accentuating the atmospheric qualities that are there in the music and the text. This was especially true tonight during the pieces by Arvo Pärt, which have considerable dissonance and frisson amongst the parts, with long sustained notes during which the spatial effects from the direct and indirect sounds arriving at our ears can be fully appreciated.

T aking into account the speed of sound, we can convert energy defocusing in the time domain to “smear” in distance estimation by the ears. Energy spread over ±500 ms is the same as a distance smear of ±15 cm. 96 KS/s keeps almost all the energy within about ±50 ms, or ±1.5 cm. One of the observations people make about 96 KS/s material is that the spatial localisation of everything is very much better than 44.1 KS/s. 192 KS/s is better than this, although very dependent on amp and speaker performance to demonstrate it.”
— Mike Story, 1997.

T he spectrum of frequencies and harmonics returning to your ears in this marble-and-plaster, highly-reflective cathedral has a surprising, pleasing amount of power in the range 4 KHz and up. In an age when noise and unpleasant/irrational/blurred stimuli bombard us every day, the Tallis Scholars’ sound in this sort of brightly reverberant performance space restores our belief in clarity—restores our belief in the fidelity of human communication across large distances in space and time. It is as though high signal-to-noise ratio becomes an aesthetic and cultural emblem of Civilization itself.

W hat I mean is, the sound (with its high S/N and high-end harmonics) not only embodies the enduring and transcendent meaning of the sacred music that Tallis performs and the human spirituality that caused this music to be written so long ago, but it asserts the very possibility of transcendence and persistence—of meaning that lasts beyond one’s own lifetime. After the concert, I go to Gimell Records’ website and download a couple of their 24-bit 176 KHz-sampled Studio Master high-def recordings, to get more of this. What I hear is truly thrilling—as good as the live performance.

C onventional wisdom doubts that humans can hear frequencies much higher than 20 KHz—frequencies higher than that are only perceptible to dogs and other animals. That is foolish—misinformation propagated uncritically since 50 years ago. In recent years, the misconception persists as a reflection of the fact that otolaryngologists’ and audiologists’ primary focus has been on “basic,” “practical” functions such as a person’s ability to hear and accurately understand speech. By contrast, research concerned with aesthetic and musical functioning has received much less attention or funding. [Measurement equipment for studying acoustics of bats in the 20 to 100 KHz part of the spectrum has existed for quite awhile—bat and bird and other animal communication is the subject of scholarly articles in acoustics society journals—but not many researchers studying humans have utilized it. Part of the reason why the freqency spectrum above 4 KHz for vocalizations has been under-studied is that high-speed video strobolaryngoscopy has been unable to detect the very small-amplitude (~0.1mm) vibrations in the larynx. Not surprisingly, if you can’t detect something, then you tend not to study what you can’t detect.]

T here is a common, mistaken notion that frequency response above 10 KHz is only relevant to sibilant “S” or fricative “F” type consonants in speech or singing. Well, that is most definitely not true, as evidenced by tonight’s Tallis Scholars performance! Recent research by Brian Monson, Andrew Lotto, and colleagues at the University of Arizona in Tucson (link below) shows that the frequency spectrum above 8 KHz figures prominently in singers’ sustained-vowel sound imaging—and figures also in listeners’ perception of open vowel sounds. The Pärt works in tonight’s program—and the effects of reverberation in these, in Immaculate’s chancel—especially emphasize intervallic and spatial relationships and transformations, and remind me of a workshop led by John Roeder at the 2003 Mannes Institute. That workshop examined expressive transformational representations for music by Pärt and others, and addressed how transformational representations relate to musical form, and to how musical forms are experienced. Varied repetition as in Pärt amounts to retracing similar transformational pathways among different sets of musical objects, and plumbing the extent and meaning of their similarities. Canon and contrapuntal cyclical spaces are frequent vehicles for enacting or showing transformations, of course, and—to the degree that each of these enactments is individually convincing—uncovering these unexpected connections becomes our primary mode of understanding and enjoying the music.

T onight’s performance and these HD Gimell/Tallis recordings reveal why it’s desirable to have a sampling frequency that is at least 4 times the desired system bandwidth, a process that is known as oversampling. If your goal is to maintain a “flat” response with 6 dB or less roll-off at the upper limit of the band, then a sampling frequency that is more than four times the desired bandwidth is needed—hence, the 176.4 KHz or 192 KHz sampling rates on these Gimell HD Studio Master files.

A problem (for me, at least) with off-the-shelf HD audio equipment is that the sound reproduction chain (player, preamps, EQ, power amps, speakers) can sometimes have too much high-frequency power. It can sound too sibilant—even for vowel sounds—somewhere between 12 KHz and 20 KHz. The spectrum EQ sliders on your playback equipment may not have center frequencies that correspond to wherever that objectionable tweeter “break-up frequency” peak is—so the adjustments you make to cope with it end up impairing the quality of the sound around that peak, essentially leaving you with a sound that's far less than HD. But Bowers & Wilkins speakers are one example of a product that doesn’t have this issue. They’re clear above 8 KHz, and give smooth mid-range and ample bass. Put two 800 Diamonds in front of you, two 802s behind you, plus a couple of DB1s somewhere in the room to cover the bottom bass frequencies. HD music recordings—such as those produced by Tallis and Gimell—have frequencies that exceed 20 KHz and we need speakers (and other components in the reproduction chain) that can accurately render these. The response of the 800Ds is essentially flat between 25 Hz and 33 KHz. Their tweeter “break-up” frequency is way, way out of harm’s way—at about 70 KHz.

R eproducing high frequencies has everything to do with recreating the sensation of sharpness and immediacy—the experience of being near the sound-source, in or near the front row (see Beranek, p. 511). There is not just the issue of rapid attenuation of high-frequency portions of the spectrum as a function of distance, but also the matter of inter-aural time-difference cues.

W e found that robust pitch perception can be elicited by harmonic complex tones with fundamental frequencies below 2 KHz, even when all of the individual harmonics are above 6 KHz—well above the currently-accepted ‘existence region’ of pitch and above the currently-accepted limits of neural phase-locking. The results suggest that perception of musical pitch at high frequencies is not constrained by temporal phase-locking in the auditory nerve but may instead stem from higher-level constraints shaped by [immediately] prior exposure to harmonic sounds.”
— Andrew Oxenham, Christophe Micheyl, Michael Keebler, Adam Loper & Sébastien Santurette, Dept of Psychology, Univ Minnesota, 2011.

I n other words, our ability to perceive (a) spatial relationships—relative locations of different singers or depth and breadth of other sound-sources—and (b) overtones/harmonics generated by the blending of all of the lower frequencies in ensemble (Fourier spectra of mixed signals) ... depends primarily on the high-frequency (short-wavelength) components and on phase-angle relationships between the frequencies as they mingle with each other in the performance space (or the playback environment, for a recording). If the sound-sources are moving (as in an opera; or even for singers who are shifting or rotating slightly on-stage), then the high-frequency components contribute most to our ability to perceive that motion. It’s part of how our brain sorts out “signal” from “noise” in noisy environments.

A nd we get special pleasure from successfully doing this. Clarity that facilitates the listener’s own brain’s processing—which is what the HD 176 KHz/192 KHz-sampled media does for us (see Vorländer, pp. 222ff).

Jan Pieterszoon Sweelinck - Hodie Christus Natus Est
John Taverner - Magnificat (A5)
Robert White - Tota Pulchra Es
Arvo Pärt - Magnificat
Arvo Pärt - Nunc Dimittis
Hieronymous Praetorius - Magnificat IV
Robert White - Regina Caeli
Morales - Regina Caeli
Benjamin Britten: Hymn to the Virgin
Giovanni Pierluigi Da Palestrina - Magnificat for Double Choir
Giovanni Pierluigi Da Palestrina - Nunc Dimittis for Double Choir

I very much hope that Phillips and colleagues continue to add aggressively to their HD DVD-Audio recording downloads. There are many of us out here who crave the immersive psychoacoustic experience that only very high sample-rate HD can deliver. The Tallis Scholars’ recordings are [one of the types of—] music that powerfully motivates and intensely satisfies the “immersive HD” desire.

B efore you place an order, Gimell recommmends to try the Test Files they provide for free download, to insure compatibility with your system.

T allis and Gimell recommend using an audiophile-quality Network Music Player to listen to the HD download files. If you own a DVD-Audio player and your PC has a DVD burner, then you can create your own DVD-Audio discs by importing the HD download files into Cirlinca’s DVD-Audio Solo® or other similar software apps. The files are 15 to 18 times larger than the equivalent track with MP3 compression. The Gimell offerings also include multichannel Quadraphonic/Surround Sound formats. Cirlinca’s HD-Audio Solo Ultra® v4.1 software costs just USD$75 for a single-user license— HD-Audio Solo Ultra® is the product that I use. Cirlinca has relationships with record labels including Gimmel, Deutsche Grammophon, and Hyperion, plus orchestras and ensembles including Boston Symphony Orchestra, Philadelphia Orchestra, and many others.

M arketing-wise, when HD recordings such as these from Tallis/Gimell are coupled with correspondingly good playback chain equipment it opens up a promising (and to-date under-developed) market segment for serious music: tech-avid audiences and software developers and gamers whose primary passion is virtual reality (VR) and who have a strong but decidedly secondary interest in music. Many in this segment or niche market may not be musicians per se, and they may not be people who regularly attend ‘conventional’ live concerts. But they crave excellent VR and immersive “worlds” that can capture the heart and mind—as good music can do so effectively. And such people spend quite a lot of money each year on personal “world-building”. Their sort of passionate “sonic-experience-first-music-second” amateurism is, I suppose, not unlike serious HiFi audiophiles of the 1960s or late 50s.

I n summary, Tallis Scholars and Gimell are creating the right kinds of HD content to grow a VR audio market. Maybe more and different marketing, including social media, will be needed to really drive its growth. For now, I’m delighted to have experienced these wonderful recordings that prove once and for all that very high sampling-rates of 176.4 KHz and 192 KHz are actually necessary, to accurately reproduce the nuances that we hear up-close in live performance. The freshness and lightness and clarity of the sound invite the listener “inside” the world that the music conjures—the Studio Master HD files enable listeners to inhabit that world via interactive replay evoking “live” sensations and realism, most vividly when the listener/file-downloader can freely explore and re-explore again and again ad lib. We avid listeners want to rehearse our neurons—not only to re-experience the shivers up our spines, but (through practice) to train our bodies to optimally respond to the aural cues that are in these beautiful HD recordings, and in the next live performance we’re able to attend. Bravo!

Wednesday, January 19, 2011

The Importance of [a modest number of—] ‘Wrong’ Notes

Authenticity is not the only quality for which a performance might be valued. Where a relatively inauthentic performance is highly valued, it is valued in spite of its ‘inauthenticity.’ For example, Schnabel’s recorded performances of the Beethoven sonatas are well regarded despite the wrong notes that they contain.”
— Stephen Davies, p. 47.

Beethoven marks ‘fugue in 3 voices with some license’, which is a serious understatement [Sonata No. 29 in B-flat Major, Op. 106, “Hammerklavier”] and which I read as something of a joke: the joy of the joke being the extent to which Beethoven will simply flaunt the very idea of a fugue. Though the fugue subject begins with a series of consonant, descending thirds (taking up an obsessive theme of the piece as a whole), pretty soon its running sixteenth notes have a willful tendency to encounter all sorts of dissonant neighbors, and these ‘wrong notes’ become a subject for the composer’s perverse and inventive discourse. Beethoven’s ‘play’: causing all kinds of collisions of one dissonant neighbor with another and then miraculously making sense of them: this is the playful creation and resolution of chaos.”
— Jeremy Denk.

I was recently checking to see how my friend, pianist Victor Goldberg, is doing with his Asian tour. As part of my online “checking up,” I looked at his Twitter feed, which I had not done in awhile. There was not much in the way of updates about his performances in Hong Kong or Taiwan or Thailand in there, but there was this little tweet from last June, which I’d not previously seen.

Are wrong notes that important?”
— Victor Goldberg, Twitter, 23-JUN-2010.

N umber one, Victor plays exceedingly well, with wonderful expression and technique. He does not produce wrong notes—at least not many of them, and especially not many of them in the context of the difficult, finger-challenging repertoire he performs. His tone remains consistently focused, clear, and centered throughout the range. The pulse remains secure, and his rhythms are accurate for the style. Dynamic levels are consistent, emotionally coherent, and an accurate interpretation of the style. Phrasing remains always consistent and sensitive to the style. Expressiveness manifests creative nuance and style, remaining responsive not only to the score but to other performers and the audience. Articulation has secure attacks, and all markings (staccato, legato, slur, accents, etc.) are executed accurately. In short, anyone who has heard Victor play would be astonished by his Tweet from last June.

N umber two, Victor’s recoveries from any notes he misses are invariably graceful and, if anything, the few misses lend in an admirable way to the overall humanity of his performances. We do not attend to hear damned automatons or computers perform. We come to hear a real human, and to vicariously experience our own humanity more fully through what that dear human does.

N umber three, we know both the quotidian and the sometimes noble, poignant origins of “mistakes” in elite performers; we understand how they happen, at least those of us who have ever studied music do. And we actually want to witness them. We love virtuosic spectacle, yes, but, more than that, we glimpse first-hand in the virtuosos’ limits and accomodations and recoveries from occurrences around those boundaries some important dimensions that we have and that all people, past, present, and future have.

N umber four: authenticity is not conditioned upon enslavement to the urtext. In any good performance, we witness improvisatory but at the same time fully consequential music. We see the person’s full absorption as it unfolds in front of us. And, given the finiteness of human attention and other capacities, the “full absorption” is not evenly spread across all of the myriad elements to be attended to. As a result, we witness the highly personal irregularities of the elements that receive extra attention, while other less-attended elements recede toward the boundaries where the so-called “mistakes” happen. A lot of what we call “depth” in performance arises via these core-vs-boundary processes. Again, it is part of the beauty.

N umber five: the composer created these risks in the score. In some cases the risks were put there deliberately, in full recognition of what awkwardnesses under the hand (or for the voice, etc.) would do to the performer—some of Rzewksi’s writing is diabolical in this way—and in other cases it was happenstantial/incidental. But the aesthetic whole—the unity of the score’s architecture, replete with its hazards and insurmountable challenges—is what we seek.

N umber six: We can measure the “mistakes” and statistically model the ‘reconstruction error’ or fidelity to the score. In principle, we could study the situations in which the reconstruction error density is high and yet our emotional and aesthetic reception of the performance is also [paradoxically] high.

F irst, we record the occurrences of deviations from the score and transform them from the time-domain to the event-frequency-domain. Then y_t is the power spectrum of those deviations. And we calculate the Kullback-Leibler (KL) divergence (see Lee and Seung 1999)… the 50-cent equation up at the top of this blogpost.

F or those who are especially interested in these issues, have a look at the paper by Maria Ruiz, Hans-Christian Jabusch, and Eckart Altenmueller at Hanover and Dresden (link below).

N umber seven: some of what we hear as “wrong” is not wrong after all, even if the performer herself/himself obsesses over it.

W e first have to diagnose the right notes as ‘right’ before we can say that any of them are wrongly played—‘diagnose,’ rather than merely find: no longer does the fact that a composer puts down a C on paper [or in Finale or Sibelius, etc.] necessarily mean that s/he cares two hoots if a C sharp is played instead, or a C-semi-sharp for that matter. And even if s/he thinks s/he cares, one takes leave to doubt the profundity of his/her worries when, in rehearsal, one notices that s/he does not perceive the difference between the alleged right note and the wrong note s/he gets instead.”
— Hans Keller.

E vents remaining in Victor Goldberg's Asian tour include:

Masterclass, City Hall, Hong Kong - 20-JAN
Masterclass, Hong Kong University - 21-JAN
Concert, Discovery College, Hong Kong - 23-JAN

B est wishes, Victor. See you back in the U.S. at the end of the month.

Saturday, January 8, 2011

AntiPatterns: Classical Banjo, Code Refactoring, and Short Time-scale Acoustical Physics

O ne has merely to hear the banjo’s strings touched, or one double-stop drawn out on the fiddle, to recognize the sense in which the meaning of bluegrass begins simply with what these instruments essentially are: it is the aim of bluegrass style to set forth what the instrument—or for that matter the person playing the instrument—essentially is.”
— Robert Cantwell, Bluegrass Breakdown, p. 203.

A thousand kilometers away, one of my nephews is tackling learning banjo. I give him Bullard’s book (link below) and begin listening to exotic recordings by Bela Fleck and John Bullard and others, in hopes of having mutually fun dialogues with my nephew, via email and face-to-face when I go and visit him.

T he banjo sounds on these recordings remind me of the sound—the ‘interiority’, the ‘earnestness’—of traditional shamisen or samisen (三味線, literally “three-taste strings”) music. Shamisen is similar to banjo in that the dō, the skin-covered box, is a lightly-damped resonator, much like the banjo’s. Both instruments are highly percussive and relatively ‘bright’. Both are plucked with the fingers or with a plectrum.

S o I go looking around to see what spectral analysis studies have been published about banjo or shamisen. I am curious to better understand the reasons that explain the unusual tone or timbre of each. Välimäki and coworkers spent a lot of effort on the matter in the mid-1990s (link below). Unlike guitar and other stringed instruments, for banjo the 5th harmonic (fourth overtone; 2P8+M3) and higher harmonics are rapidly attenuated, except for the 8th harmonic (3P8; 3 octaves above fundamental).

S olid body electric guitars don’t lose much string energy to the bridge. As a consequence they have a distinctive sound and are very long in sustain. Banjos on the other hand dump energy from the strings very easily to the rest of the instrument, and their characteristic sound is in large part related to that.”
— Liutaio Mottola.

T he directionality of the instrument’s sound radiation has a lot to do with banjo-ness, too, I think. Plucked string instruments have complex sound radiation patterns for various reasons. The resonant-mode frequencies of the box account for most of the radiated sound pressure. And different mode frequencies of the body have their own directional patterns, such as monopoles, dipoles, quadrupoles, and their combinations (see examples at UNSW, Joe Wolfe’s site, link below).

A nother distinctive factor is ‘masking’ caused by occultation of the sound by (and reflections from) the performer’s body. Masking plays an important role in environments where the listener (or the recording microphones) and the sound sources are positioned off-axis from each other or are freely moving with respect to each other.

T he influence of “X” vs. “Y” hand position for passages that involve the right-hand moving up the neck of the instrument is yet another factor, one I must remember to explore with my nephew when I next see him. The “X” position lends a bright timbre, and the “Y” position gives a rounder, darker quality. What the the player does with the right-hand on the head of the banjo also changes the timbre/color a lot.

A nd then there is picking technic. Fleck’s jazz-influenced single-string picking style lends an extra “impulsion” to the banjo timbre—a consequence of sympathetic acoustic coupling to and from the other un-plucked strings? The “impulsion” is one of the qualities that I am most attracted to in these recordings.

O h, the sheer exoticness of them, though! The sound calls into question the locale, the culture and politics, and the epoch of each musical text and of each of the speakers (composer, performer) and hearers. The ‘rurality’ of banjo timbre... the instrument’s architecture preserved even in the most refined, expensive ones of modern manufacture with technical polymer engineered-composite materials and high-tech strings.

T he ‘interiority’ of chamber banjo sound is radically different from the interiority of lute or harpsichord. If our own interiority is an object, then the music embodies that ‘objective’ world. Not ‘mimesis’ or ‘representation’; more like incarnation...

P hysical strings vibrate in both the vertical and the horizontal directions (well, actually, more like a lissajous curve in the plane perpendicular to the string’s length, so the polarization directions are changing and are only intermittently orthogonal to each other). If the effective length of the string is not the same in the two predominant polarization planes, we get mixing of the subsignals of slightly different frequencies, which in turn creates beat-frequency pulsations in the sound. This is a distinctive feature not only in banjo but in the Finnish kantele’s timbre as well, where the mechanism has to do with the peculiar way in which the strings have been terminated on the box.

V älimäki and colleagues emphasize that distinctive timbral properties of banjo are associated with the “attack”, the early transients in the waveform in the few tens of milliseconds immediately after the string is plucked or frailed. But there are wonderful, deeply banjo-ey aspects in the notes’ “decay” as well. We hear those in the Bullard and Fleck recordings. The ‘openness’ of these transcriptions of baroque, classical, and romantic compositions affords closer examination of those timbral spectral features than would ordinarily be possible to do in, say, idiomatic bluegrass and other banjo repertoire.

I t seems to me that these recordings of Bach and other composers’ works on banjo draw our attention to what neurophysiologists call “event fusion” (the formation of unitary musical events from the micro-evolution of waveforms on a time-scale of tens of miliseconds, too small to exhibit rhythm or voice-leading) and its inter-relationships with harmony and melody and rhythm and larger-scale form.

T hese banjo transcriptions and arrangements are unusual, musically speaking, but they register for me as very familiar in other ways. ‘Refactoring’ and ‘porting’ musical “code” from one performance “platform” to another—in the manner that Bullard and Fleck exemplify—feel to me very much like refactoring and porting computer code from one computing platform/language/operating-system/architecture to another. The process calls into question the [psychological; physical] conditions necessary for making large-scale—that is, ‘formal’—interfaces and system services-stack clear in music, just as the refactoring process does in software. The process in both cases invites or even demands reconsideration of the work’s design constructs and architectural components.

I n both, it vividly reveals the different levels of abstraction that are supported or not-so-well-supported by the different platforms. And it can uncover the essence of our interior selves, by making us pay attention to neural logic-races, multi-timescale communications phenomena, and hard-coded “antiPatterns” that the composer or performer (or listener) might not otherwise have noticed. So even if the target transcribe-to platform (banjo) manifests some antiPatterns of its own, it is still always healthy and illuminating to be outside our “comfort zones” and gleaning what we can from the refactoring process.

T he beauty and elegance of these classical banjo recordings make me want to revisit some of my own code that I have recently [re-]written; improve it; maybe understand it from novel and useful perspectives.

A ll sounds, all colours, all forms—either because of their preordained energies or because of long association—evoke indefinable and yet precise emotions, or, as I prefer to think, call down among us certain disembodied powers, whose footsteps over our hearts we call emotions.”
— W.B. Yeats, The Symbolism of Poetry.

H ow can we know the dancer from the dance?”
— W.B. Yeats.

Saturday, December 4, 2010

|| Eye Candy + Ear Candy || ≤ || Eye Candy || + || Ear Candy ||

Burtner’s ‘A’aa’, Grace Lai, flute, and Michael Abrams, clarinet

Grace Lai (flute) & Michael Abrams (clarinet) perform Matthew Burtner’s ‘A’aa’ at KcEMA event at La Esquina in Kansas City (03-DEC-2010)

H ow much information is carried in [neural] spike trains? Should we use the discrete theory or the continuous one? Spike times are not discrete, and discrete calculations don’t seem to give satisfactory answers. But, on the other hand, the continuous theory assumes a continuous space, and, from the available evidence, that is clearly too strong an assumption to be valid. What, then, is the [mathematical, topological, metric] space to which spike train phenomena belong? While it might be possible to define the sum of two spike trains by simple linear superposition, it isn’t at all obvious how to define the difference. There is no reason to expect spike trains to be Euclidean. For example, with regard to color perception, MacAdam ellipses in color space are wildly non-Euclidean.”
— Conor Houghton, Trinity College, Dublin.

T he acoustic and optic stimuli we received at the KcEMA event held last night at La Esquina in Kansas City were intense, sensorially immersive, emotionally evocative, and thoroughly satisfying in terms of their well-crafted dramatic arcs, accessibility, and comprehensibility. The seven works performed were selected from among 120 compositions that were submitted by composers from around the world, in response to KcEMA’s call-for-scores last Spring.

Elainie Lillios (composer), Bonnie Mitchell (visual artist) – “2BTextures”: 2-movement work of abstract animation “takes the audience on an integrated sonic and visual journey into a surrealistic environment influenced by Nature.” This is an edgy, edgy piece with extensive, dramatic use of surround-sound spatial movement of sound, around the Mackie speaker array that was deployed around the perimeter of the audience seating area. The computer-generated visual displays were very high-dimensionality animations, with many tens of thousands of dynamic objects projected in motion at each moment.
Bret Battey (composer, videographer) – “Sinus Aestum”: inspired by the eponymous plain on the Moon’s surface, smooth and dark, “articulated by threads of white dust, like the tips of flowing waves.” Music and video sequences are propelled by algorithmic processes that sample the digital imagery of surface topographic XYZ structures of this lunar plain. It reminds me of ‘Swarm’ software, with autopoiesis and phase-transitions generated by adaptive networks of communicating processes, much like nonlinear reaction-diffusion equations in statistical physics and chemistry, such as the Belousov-Zhabotinsky reaction and other processes in non-equilibrium thermodynamics. Composer as Dawkinsonian “blind watch-maker” impersonal God, initializing the universe and letting Creation auto-unfold as it may. This is utterly phenomenal and without doubt one of the most elegant unifications of light and music I have so far had the pleasure to experience. Bravo!
Matthew Burtner (composer) – “A’aa”: includes field recordings of lava flows and associated sounds emitted by an active Guatemalan volcano, and expresses deep ecology at a primeval, violent, chaotic, low frequency-spectrum, butt-thumping level via the Mackie SRS1500 subwoofer—convincingly conveying the notion that human affairs are puny compared to stochastic geophysical mechanical processes: not only beyond our control but largely beyond the reach of human technologies even to monitor or measure or predict. Burtner’s Nature is uncaring; however, it is not malevolent. It does not wreak shock and awe on all sentient life-forms, human and otherwise. Instead, the shrieks and rumblings of the Earth pushing viscous molten rock are surprisingly benign; nothing is imminently about to explode; this Guatemalan volcano is somewhat like standing very close to a powerful waterfall that is not going anywhere and is not going to kill us. The lava cools, creating solid crusts, and these smash together under the pressure of still-molten material behind them, generating breaking, shattering sounds. [I very much liked the percussionist, mashing fist-sized lava rocks together. The miked grating, smacking sounds of these added high-frequency effects on top of the thundering volcano sounds. Grace Lai’s flute and Michael Abrams’s clarinet, both playing long, sustained notes with pitch-bending and harmonics rounded out this ecoexperience, complementing the timbres of the realtime volcano sounds.]
Jeffrey Hass (composer), Elizabeth Shea (choreography) – “Magnetic Resonance Music”: composed after his having an MRI exam, during which he “focused on bizarre, strident, extremely loud noises and complex rhythms the machine was making.” The world according to Hass has humans as guinea pigs, to whom things are done or happen passively while doctor-priests tell you to hold perfectly still. Shea’s choreographed movements are wonderful counterparts to Hass’s impulsive quasi-chaos syncopated music. Very cool!
Christopher Burns (composer) – “Sawtooth”: mash-up of elements of visual performance and sound-art. Instead of a personal sensor-area network with transducers capturing biomechanics signals from a live performer’s limbs and trunk (3-axis accelerometers, gyros, joint goniometer angles, etc.), Burns uses the video camera on the LCD monitor of his laptop computer to capture the motions of his arms and torso and hands, which he moves Theremin-style . Scene-recognition, edge-detection, and vector velocity computations from the realtime video image datastream of motions of the performer captured from the camera are translated in software and converted into both music and visual animation. The gestures are transformed into a rich palette of pitch set and crescendo/decrescendo and articulation and other motifs. Simultaneously, the gestures yield an interesting range of optical and animation effects, projected on the walls of the performance space. The spatial positions and colors and intensities and sizes (scale) where newly ‘launched’ animation objects appear depend on the position and speed and direction as well as ‘open-hand/closed-hand’ morphology of gestures that Burns makes with his hands. The result is a truly beautiful, cohesive integration of sound and light. [Just as with the recent ‘Faster Than Sound’ event at Aldeburgh, there are issues regarding our less-than-optimal notational idioms for scoring complex computer/electronic music – video/light-show compositions, to sufficiently specify what comes precisely when and specify interfaces for multiple disparate acoustic and optical effects in technology-interoperable, manufacturer-independent ways – so as to facilitate future rehearsals and performances by persons other than the composer/video artist/dancer(s) and on the equipments of future decades when the computers and other devices and patches we now have are long-since obsolete.]
Robert Ratcliffe (composer) – “Phoenix”: repeated resurrection from sonic ashes “explores the possibility of combining characteristic features of synthetic‐driven electronic dance music genres such as acid house and techno” with elements of instrumental and electroacoustic composition. I am reminded of the sounds that titanium robot insects make during the raves that precede their exuberant mating season. This thing is absolutely danceable—very, very nice.
Mike McFerron (composer) – “Prelude to You Brought This On Yourself”: sonically explores the physical and emotional abuse experienced by an openly homosexual youth, and “attempts to comment on a human collective intolerant of an individual voice, who is not asking to be understood or even heard, but simply allowed to exist.” The tintinnabulations of small bells are synchronized with images of people that flash in front of us, accompanied by short voice-over recordings, mostly of anti-gay hate-speech by conservative religious figures. This is a deeply moving, powerful testament to the courage and resilience of those who are harmed—be prepared to be moved to tears as you listen and watch: no mere electronic music or multimedia installation work, it is a galvanizing, effective example of art as political intervention to bring about a more just society.

Battey—‘Sinus Aestum’

W hy do light shows combined with music affect us in ways that are substantially different from either stimulus taken separately? Are there features of dynamic light displays that, when designed and synchronized with music, might optimally stimulate our senses and enhance the depth of our reception of the music?

I s there a point of “sensory overload” or “diminishing returns” as regards multi-sensory stimulation to accompany music? Conversely, why do periods of silence or darkness that sometimes arise in electronic music / lightshow events cause hallucinatory acoustic and optical experiences? How might composers understand and leverage these neurophysiologic phenomena to better advantage, expressively?

M ight there in the future be implantable prosthetic devices—or legal, safe, and effective “performance-enhancing medications” (esp. glutamatergic ones or GABA-ergic ones, to modulate corticofugal transmission)—that could further enhance or extend the scope of these tandem multi-sensory experiences?

W hen I fly on long trans-oceanic flights and listen to my iPod, my perceptions of music are distorted, sometimes in interesting, revelatory ways. How, if at all, would combinations of music and light in zero-gravity space environments differ? Could space-tourism include specially-composed music and accompanying light displays that would capitalize on the sensory biophysics anomalies up there, to produce an extraordinary kind of transcendence for the travelers?

M ight electroacoustic music-light compositions in the future be composed so as to be more effective for music therapy purposes, compared to current conventional “music-only” music therapy?

H ow do the experiences that people with autism-spectrum disorders have of light-sound compositions differ from others’ experiences?

T hese questions occurred to me last night as I listened to the performances of electroacoustic and computer-based compositions at La Esquina in Kansas City. (The same questions had dogged me when I attended last month’s ‘Faster Than Sound’ event in Snape.)

Burns – ‘Sawtooth’

N eural coding has traditionally been assumed to be one of rate-coding: the stronger the stimulus, the more action-potentials per second that a sensory neuron transmits, and the stronger the perceived sensation is.

H owever, it’s now known that in various sensory systems there is ‘sparse temporal neural coding’. The timing and univariate temporal pattern of action-potentials and sequences of clusters of them in a single neuron itself carries information. The bivariate or multivariate temporal pattern of concurrently-incident action-potentials in multiple neurons, which may perhaps be in different sensory pathways (such as acoustic nerve and optic nerve pathways, thalamic pathways, cortical pathways, etc.) may likewise carry [different] information.

T he processing of sensory information by the brain is difficult to understand, in part because of complex interconnections between the sub-cortical and cortical areas. connections between the thalamus and the cortex in the brain are reciprocal, with information carried both in “feed-forward” [peripheral nerves to thalamus to cortex] and “feed-back” [cortex to thalamus] directions. Sensory signals reach the cerebral cortex after having traversed many synapses along multiple pathways. Acoustic and optical signals interact in the thalamus and possibly elsewhere, in both mutally excitatory and mutually inhibitory ways.

C onor Houghton at Trinity College, Dublin, has recently examined spectro-temporal receptive fields and filter functions in studies of the neurophysiology of bird song, using analytic formalisms of van Rossum metrics and non-Euclidean spaces. Useful, I think, for human music analysis, and not just of multi-sensory music-visual works...

A nd Stephen Coombes’s and Paul Bressloff’s edited volume (link below) covers how the patterns of spiking activity provide a substrate for the encoding and transmission of information, that is, how do neurons compute with spikes? It is likely that an important element of both the dynamical and computational properties of neurons is that they can exhibit bursting, which is a relatively slow rhythmic alternation between an active phase of rapid spiking and a quiescent phase without spiking—which is altered by “cross-talk” (statistical cross-correlations) between the spiking patterns evoked by concurrent stimulation by music and light.

W ith regard to the ‘sensory overload’ question, there is a fair amount of recent research that is germane to this. In mathematics, the triangle inequality is a defining property of norms and measures of distance. This property must be established as a theorem for any function proposed for such purposes for each particular space. For example, the triangle inequality holds for spaces such as the real numbers, Euclidean spaces, L^p spaces (p ≥ 1), and inner-product spaces. Maybe it also holds for multidimensional perceptual spaces, such as ones involving simultaneous stimulation by sound and light.

E ven if these are one-of-a-kind experiences never to be quite the same twice, and even if the communication impact of multisensory stimulation is subadditive in terms of quantitative neurophysiology and biophysics, the qualitative expressive and aesthetic result of any particular performance can nonetheless be really, really wonderful. Congratulations to each of these composers/artists/performers on these fine compositions and ‘sensorially whelming’ performances at KcEMA!

M usical Ecoacoustics embeds environmental systems into musical and performance structures using new technologies. Ecoacoustics derives its musical procedures from abstracted environmental processes, remapping data from the ecological into musical domain. It draws on techniques of sonification, acoustic ecology and soundscape composition (e.g, Truax, Westerkamp, Keller and others). The data from nature may be audio information (from wind or ocean waves, for example), or it may be a signal produced from some measurable parameter such as temperature timeseries, geological change or seismic data, astrophysical data, and so on. Going beyond mere direct sonification, the composer develops a syntax on the basis of the recorded natural processes, and creates new patterns conforming to this syntax.”
— Matthew Burtner on ecoacoustics.