/ A Dynamic Model of Metric Rhythm in Electroacoustic Music
A Dynamic Model of Metric Rhythm in Electroacoustic Music Jeff Morris Center for Experimental Music & Intermedia, University of North Texas Jeff.Morris@HBProductions.net Abstract The possibilities offered by electronic composition tools, while liberating, make difficult the dynamic use of organized rhythm in electroacoustic music. This paper explores a model stemming from interactive electroacoustic work by the author that adapts aspects of the hocketed, disjunct rhythmic textures of funk styles for use as a developmental musical parameter. These methods for generating rhythm that facilitate transformation in ways more naturally manipulated by computer-based tools are demonstrated in theory and in use by the author. 1 Introduction Modern electronic tools for music composition allow a practically infinite variety of time relationships; however, this freedom has made it difficult to organize rhythm as an active developmental parameter of a musical work. Most tools either leave composers adrift in a practical continuum, or force them to wrestle with (or settle for) conventional eighteenth-century metric patterns. A common solution is to use a multitrack audio production tool that allows metric grids to be placed over a temporal continuum. It is possible for multiple sounds to be organized according to different metric grids, but each grid is static, is limited to conventional meters, and makes for tedious work placing each sound. After bouncing a static rhythmic passage to a single file, a phase vocoder or granular sampling application could be used to warp the rhythm in controlled ways, but the attack envelope of the sounds would be distorted as well. Some applications offer a tempo map in which time can be warped without distorting the original sounds, but these tools can usually only support one (conventional) meter at a time and still require tedious placement of individual sounds. As one alternative to these limitations on rhythmic organization and development, the model presented here, developed in the Max/MSP programming environment, gives unique dimensions of flexibility and structure in electronic or acoustic algorithmic composition, in or out of real-time. 2 Theory This work was inspired by attempts to describe the principles active in musical moments that are simultaneously engaging and elusive, the combination of which evokes a special excitement in the listener. This seems to be mainly the realm of rhythm and texture, and is a key element of funk styles. The effect is achieved through a kind of balance between predictability and surprise, such that a listener is compelled to follow, despite being continually shaken loose. This is related to musical discussions of entropy (in the form of surprise; Meyer 1967): the balance is somewhere between redundant stasis and continuous change. When achieved, the effect is synergistic, as if the stimulus were much more complicated that it actually is and more exciting than the simple sum of its components. The term tickle is used here to refer to this effect of engaging elusiveness. Study of funk metric structures has revealed that the music is usually unstable at the level of the single 4/4 measure, but stable at the levels of the eighth note pulse and the two-measure segment. Whereas the former is more widely recognized, the stability of the two-measure segment comes from a tendency to disrupt every second downbeat (usually by delay or anticipation). One measure often does not look like the next measure, but one pair of measures is often very similar to the following pair. Between these stable levels is where the tickle is evoked. The quarter note beat is usually unstable; the steady eighth note pulses are divided into groups of two or three by accents. It is in the mixture of two- and three-pulse groupings that elements of stability and surprise can be manipulated. This is congruent with studies demonstrating that human perception is most sensitive to a specific range of durations, peaking around one half second (Fraisse 1963, Povel 1981). It appears that the ticklish component must be focused within this range to be effective and that it needs stability on adjacent levels to react against. pulse groups 2 2 3 2 2 1 3 ' 2 Figure 1. The guitar riff from James Brown's "Give It Up or Turnit A Loose" (1968/1996) demonstrates an accent pattern of 2, 2, 3, 2, 2, 3, 2. Note how a pulse group lies across the barline. Proceedings ICMC 2004
Top of page Top of page