Dancing Musicians

Dancing MusiciansAuthor(s): FrySource: Perspectives of New Music, Vol. 21, No. 1/2 (Autumn, 1982 - Summer, 1983), pp. 585-589Published by: Perspectives of New MusicStable URL: http://www.jstor.org/stable/832895 .

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DANCING MUSICIANS FRY

As a musician I often feel the urge to dance while playing. My fingers want to leave the keyboard and touch the ceiling or I'll want to

leap across the room unencumbered by an instrument. But as a dancer I am frustrated by the lack of control that I have of the music. I'll want to

play lead guitar, insert drum fills, or accentuate a bass line. Consider being both musician and dancer simultaneously. There are

many parallels between the two activities. Both require physical movement in relation to the acoustic environment. Playing an instrument could be described as a carefully controlled finger dance with audio feedback. Conceiving and realizing a piece may be distinct activities in both music and dance. The composer and instrumentalist of music correspond to the choreographer and performer of dance. Yet the most expressive moments in each art form often occur when an idea and its execution happen together within the same person... the improviser.

As general sound-controlling devices, traditional instruments, such as the flute or piano, have severe limitations. They must be designed with the constraint that there is a close physical relationship between the performer's played input and the sound output. In these instruments, a compromise is necessary between human movement (the controlling input) and instrument acoustics (the musical output). Happily, computers can treat the connection between their input and output much more flexibly. Any input may be independently mapped to any output. Furthermore, the kind of processing between input and output in a computer is not restricted by the limitations of mechanical- acoustical methods. The sounds of every acoustic and electronic instrument ever made and more could be simulated by complex digital



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synthesis. And sophisticated input devices could be capable of controlling this aural feast.

Imagine dance as the method of input to a computer. Imagine entering not simply arm waving or foot tapping, but the entire spectrum of human movement. Our moves comprise a large number of independent actions and a vast assortment of semi-dependent motions. The library of "motor routines" contained in the average person (not to mention the professional dancer) must be fantastic. And the librarian has been practicing all of our lives. Translating these actions into computer readable format is no simple matter. But recent developments in position and motion detectors promise breakthroughs in this area. I will describe two that approach the requirements for dancer input.

Polhemus Navigational Sciences makes a device consisting of a transmitter, a receiver, and a Nova mini-computer. The transmitter creates an electro-magnetic field that the receiver detects. This signal is processed by the computer to determine the position and orientation of the receiver. The computer produces six numbers between 0 and 4000 that correspond to the receiver's position (x, y, and z axes) and its orientation (pitch, yaw, and roll) with respect to the transmitter. These six variables are completely independent; any one may be affected without affecting the others. Furthermore, these six numbers are updated 40 times per second. Thus the series of numbers output by the computer can be used to describe the motion of the receiver.

There are limitations to the current model of this device. The receiver, while smaller than a cubic inch, is still too large to go unnoticed. The transmitter is somewhat larger. Each must have a wire attaching it to the computer, a limitation that I hope will soon be dispensed with. The position of the receiver can only be accurately determined when it is within four feet of the transmitter ( a little cramped for wild dancers). Still, this device and its offspring can provide a high data-rate channel of communication from human being to machine. A dancer could have several receivers mounted at strategic points on the body. Many motions could be described by reading the position and orientation of a receiver at the head, hands, wrists, elbows, shoulders, hips, knees, ankles, and feet of a dancer.



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Another versatile dance-to-computer input device is the TV camera with fancy software and fast computational hardware. There are machine vision programs which can draw an outline of a video image. Distinguishing limbs from each other and the torso is a difficult artificial intelligence problem. However, I am confident of its eventual solution because it is so easy for people to do.

Both the Polhemus and the TV camera, in their present form, leave something to be desired-yet the technology is advancing rapidly. Miniature Polhemus receivers mounted in shoes and sweaters or three orthoganal, high resolution, infra-red video cameras are likely to have the ability to sense a wide range of human movement soon.

For the musical output of this flexible, interactive instrument, we can rely on digital sound synthesis techniques. Digital processing of audio allows the production of noise-free sound with an extremely wide dynamic range (from silence to pain thresholds) and a resolution capable of expressing the minutest detail that we can hear. The generation of such acoustic detail takes considerable processing power. But the current generation of real time digital synthesizers can already produce quite intricate sounds. In the future, the complexity of these sounds will increase as the speed of computers continues to increase.

The most interesting component of this dance-to-music instrument is neither its input nor its output but rather the mapping between the two. The "arranger" decides which motion causes which sound. To facilitate these choices, the dance as well as the music should be partitioned into machine distinguishable parameters. Each dance parameter, a step or a position, must be uniquely identifiable by the input device and associated software. From the list of dance parameters which can be recognized by the system, the arranger will choose those which will actually be meaningful. The list of possible musical parameters will then be reduced to the list of parameters which will affect the music. This list will then be divided into those parameters which are controlled by the dancers versus those parameters which are pre-programmed by the arranger. The arranger could choose to give the dancer as much control of the music as a conventional musician has or as little as a disc jockey has! To introduce further variation, the



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correspondence between dance and music parameters may change as the piece progresses, cued either by an internal clock or by some combination of the dancers' movements.

For example, each dancer can be assigned to control one instrument. The pitch, the starting time, and some aspects of timbre of each note can be pre-set by the arranger. Since the basis for melody and rhythm are predetermined, a skeleton of the piece will survive the most disorganized demonstration of drunken dancing. The technique of storing a partial score inside the computer and modifying it with real- time input was used by Max Mathews in his Sequential Drum.

The dancer could have control of note duration, a limited range of timbre, and the direction from which the sound is perceived to emanate. The distance between a dancer's feet could determine note duration. Feet touching could signal a rest. Keeping the feet a few inches apart would translate into staccato phrasing whereas widely-spread feet would select legato style.

The height of each arm can control two aspects of timbre that the arranger assigns to that instrument. For one dancer these could be "brassiness" and "percussiveness". Another dancer's arms might mix the sounds of bagpipes and accordion. The arms hung straight down would cause silence. The left arm held up could signify bagpipe sound only. The right arm held up allows only the accordion to be heard. The perceived direction of the dancer's instrument would be indicated with a specialized arm movement as distinguished from the arm position that controls timbre. Pointing with a straight elbow and wrist would cause the sound of that dancer's instrument to come from that direction.

In addition to each dancer with his or her specific instrument mapping, some global musical parameters could be controlled by all dancers. Any dancer might modulate the key of the entire tune up a half-step by touching the floor with either hand. Tempo might vary based on the sum of the motion of all dancers. If everyone starts to dance faster, the music will catch up to them. For tempo, as in the the entire piece, all dancers have an effect, yet no individual has total control.

Dancers need not be limited to controlling audio. Several dancers could be designated to control lighting. A performance could be lit by



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tracking diffuse spotlights that follow each dancer wherever they dance. The color of each spotlight might be dependent on the distance between the dancers' hands (e.g. 5 feet=white, 4 feet=red, 3 feet=green, 2 feet=blue, 0 feet=off). A dancer may cause the next slide in a projector to appear by touching the head of another dancer. Using video synthesis, one dancer's image may be rear-projected on the dance hall's translucent floor while a second dancer's movements cause size, shape, and color modulations of the image to occur.

The arranger's job will not be finite with a sufficiently versatile system. The task of arranging (which really amounts to programming) could be greatly simplified using interactive computer graphics and a computer query system. Though complex, the dance-to-music arrangement is not critical. Every playing of the same mapping parameters will create a new piece. A by-product will be a sense of community amongst the dancers who have participated in a level of group creativity which could be made possible by the high tech tools of an intelligent and playful civilization.

In closing, I must confess that my arguments against dance as the input to a synthesizer with Chris Janney, inventor of Soundstair, helped formulate some of these ideas. I wouldn't have written this article, though, without the voluminous emotional support pervading the dance workshop at Another Place in August 1980.

Fall 1980

References Fry, "Computer Improvisation" Computer Music Journal

Vol. 4, no. 3 fall 1980 pp. 48-48. Matthews, Max and Curtis Abbot "The Sequential Drum"

Computer Music Journal vol. 4, no. 4 winter 1980 pp. 45-59. Schmandt, C. 1980 "Some Applications ofThree-Dimensional Input"

Master's Thesis, Dept. of Architecture, Cambridge, Massachusetts: M.I.T.

Winston, P. ed. 1975 "The Psychology of Computer Vision" New York: McGraw Hill.



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Dancing Musicians