Arco Logic
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Arco Logic Chris Chafe With the works on this album, I have been able to develop a musical thinking that has integrated my interests in performance, composition, improvisation and computer control. Over the period of time represented, algorithmic software opened up as a new medium for me, while in a parallel interest I found myself concentrating more and more closely on "performer chops." The computer explorations posed a paradox which, though not the primary focus of any of these works, had an interesting resonance in my work with improvisers. If a computer algorithm is thought to be "improvising" because it is running interactively and contains elements of indeterminacy, what do we call it when the same algorithm and conditions produce the very same music a second time? Digital computers, in their precision, make this the rule rather than the exception – a quality that has turned out to be crucial to my approach. There exists a parallel continuum between composition and improvisation in which I have often relied on a player’s own creative instincts on their consistency. Indeterminacy does not exist in the digital world, but it can exist for the computer composer who delegates aspects of detail to complex processes. The music in this album is made from a number of such systems (iterative, chaotic, hamiltonian) whose complexity is closely controlled. One aspect of numerical experimentation is that I can determine the threshold of determinacy with regard to compositional intent. For all these works, it was crucial to be able to repeat the results of an experiment exactly. Without stability, which at this level of complexity is only possible with digital means, it would have been impossible to develop the ideas in these pieces. With Free Motion, I began a line of works which are computer settings for improvisation (El Zorro, Push Pull) [c.f. Contemporary Music Forum]. The line between spontaneity and composition gradually began to blur here, too. While there is still variation from one performance to another, these pieces have tended to settle into a repeatable "groove" with each player that has learned them. So much so, that they are no longer improvisations, rather they are like familiar hiking trails visited at different seasons and in different frames of mind. The computer-generated works, Transect and Vanishing Point, are also products of numerical experimentation. I have systems for "mining" the results of live algorithm exploration. Useful "ore" is collected and later combined in a multi-track editing phase to create the final recording. Discography: Dinosaur Music Solera Quadro Duo Improvisation (CRC 2133) 1 Transect 12:23 computer generated (1999) Bowed string and a vocal tract physical models were combined for the sound. 99% pure synthesis, Transect is a projection into the realm of chamber music. Ingredients of line, articulation, and phrasing were developed by playing the string-larynx and the vocal tract with an artificial performer whose bow arm loosely mimics the physics of the real thing. Celletto phrases are mixed with synthesized music at one point partly as a comparison to see how well the synthesis quality stands up to the real thing. A year in the mountains of Alberta and California, and the mid-life interests of the composer, figure into the story line of the music which is, like the title, a section traversing. Control: Matlab, C++ Physical Model Synthesis: Seer Systems’ Reality (customized) editing: Sound Forge 2 Push Pull 9:11 celletto and interactive computer accompaniment (1995) Push Pull is a composed setting for an "augmented" improviser in which the computer becomes a part of the performer. Physical and musical gestures are amplified by software so that they launch into a life of their own. Playing their sound within a kind of "algorithmic performance," the soloist launches the seeds of what happens and can enter into dialogue with the textures that evolve. The work was completed during a fellowship period from the National Endowment for the Arts. NeXT workstation: control, pitch tracking, physical model and sine synthesis, digital signal processing bow arm tracking: Buchla Lightning sampler and digital signal processing: Korg Wavestation Free Motion: celletto with pre-recorded computer accompaniment (1990) 3 Mesh 4:31 4 Rubbing 3:58 5 Capture & Release 4:08 Free Motion is a duo between a freely improvising soloist and a tape composed with sampled sounds. The movements explore the phenomenon of friction which was on our minds at CCRMA during the period in various ways, from bowed string research to practical lessons in plate tectonics (the quake of '89). The work is similar in its sound materials to a previously composed tape work, Vanishing Point, but it differs in its construction. The earlier piece was composed while improvising with chaos algorithms. The phrases created this way were very active, but difficult to extend as background accompaniment as was needed for the current work. Starting with the same phrases generated in the chaos world, loops and reiterative methods were applied to make them persist or at least, sit still a little better. Free Motion has been performed by numerous different instrumentalists, most often string players. The only instruction is to "learn" the accompaniment. bow arm tracking: Buchla Lightning digital signal processing: Korg Wavestation computer accompaniment: (see Vanishing Point) 6 Vanishing Point 10:29 computer generated (1989) Vanishing Point is made of sampled, altered percussion sounds. It stretches the possibilities of what a live percussion ensemble might do rhythmically and sonically using computer control to get these effects. Three stages went into the work. First, while developing the sounds of a large percussion ensemble, I wanted to somehow preserve the drum machine quality of the sampler used. That proved easy. Secondly, a variety of phrases using the sounds were explored algorithmically using a microcomputer. Four types of phrases evolved, distinguished by their rhythmic feel. The "nature type" includes the jangling of wind chimes or scratchy sounds from a room next door. The "expressive type" has a certain drummer-like feel. The other two are engine-like "mechanical" rhythms and dream-like, "psychological" rhythms. In the last step, phrases were assembled into a final montage. The guiding notion was to play with persistence of these images, so that in the course of the piece they are being forgotten, remembered, ignored and transformed by each other. The only unique instrument that was sampled is the Stegosaurus, which I built in 1973 from a buck saw found somewhere in the Berkshires. It has plates of metal mounted along the back of a wooden box which can be bowed or struck. Spectral Modeling Synthesis software by Xavier Serra was used to extract the bow-noise sound of the Stegosaurus. The interactive panning program of Marina Bosi was used to control sound paths. Control: Mac+ running MIDI Lisp sampler: Sequential Circuits Studio 440 post-processing and editing: Yamaha DMP11, Studer/Editech Dyaxis 7 Backtrace 8:45 celletto and interactive computer accompaniment (1988) On-the-fly algorithmic accompaniment embellishes material played by the soloist, orchestrating and echoing notes which it detects. The soloist’s score is loosely based on a traditional Japanese composition for shakuhachi. control and tracking: Mac+ running MIDI Lisp, IVL Pitchrider, Yamaha MCS2 FM-synthesis and digital signal processing: Yamaha TX802 and DMP7