ELECTRONIC/COMPUTER MUSIC NEWS by Jim Horton
Given the chance probably any object form mood emotion category pattern person group cult attitude concept process perception event device fact instrument activity etc. can be interacted with or interact in a distinctly musical way. (John Weiss, for instance, spent weeks tuning the engine and transmission of his VW bus until it sounded remarkably like the other music he had done on Moog synthesizer.) But this column is especially about how electronics and the ideas associated with electronic systems can be used by new music players and composers. I find electronics interesting because it seems that the clear effect of the semiconductor industry is to invent and mass-produce circuits the widespread use of which could radically transform our civilization and change the definitions we give ourselves about what it means to be human. If it's possible to build automated composers, orchestras, instruments and listeners which are as musical as we are and then some, what then?
John Bischoff has been working on a composition that is relevant to this question. In the anthology Break Glass in Case of Fire, John describes a type of phenomena in which he is interested. He writes that "a momentary tuning of two environmental sounds generates the impression of one large acoustic space." He illustrates with a drawing showing a human figure standing at the intersection of sound waves coming from a car to the side and an airplane overhead. "As these auditory images arise and disappear and go from one to another a sort of harmonization (the forming of fundamentals) takes place."
John incorporates features of this phenomenon into a wider context of social listening. In his April 14th concert at Mills College he has presented a composition that utilizes a micro-processor-implemented automaton that furthers his involvement with environmental sounds. One element of the piece is the computer egolessly simulating the hearing of sounds and patiently indicating to concert-goers how an environmental melody occurs, by adding harmonic tones to the music it perceives.
By constructing an impersonal electronic device to carry out this function a possible confusion of reference is avoided. If performers were to constantly point out how sounds were happening it might be easy to think the piece was about human skill rather than about the way sounds actually occur in our surroundings.
In Bischoff's piece, two stereo tapes are prepared before-hand, each having a prerecorded environmental sound on one track. On the other track is recorded a hand-tuned square wave oscillator playing a by-ear approximation of the pitch of the environmental sound, forming a representation of the pitch content of the sound on the matching track. These square wave signals are analyzed by the computer, and whenever their pitches stand in simple interval relationships the computer responds by playing harmonically related tones.
The computer also checks to see if the pitches being heard are close to standard piano tuning and if they are it selects one of them and writes its name (c, Db, D, etc.) into a seven-segment display to be viewed by a keyboard performer.
But how does a computer "hear" the pitches? The data about the period of the signals (which is the inverse of the frequency, or pitch) is compared by cross multiplication to a table of simple ratios contained in the computer's memory. For example if signal A=2000 microseconds (500 cps) and signal B=3000 microseconds (333 cps) and the list of ratios the computer is searching for is 1:1,5:4, and 3:2, the program will first do: 1 * 2000= 2000 and 1 * 3000= 3000 and then compare the results of these multiplications. Finding they are not equal it will go on to try the next ratio (5:4) by multiplying 5 * 2000=10,000 and 4*3000=12,000. When it gets to 3:2, it finds that both multiplications equal 6000. now it knows that the two sounds have momentarily tuned into a 3:2 interval (perfect fifth). If the program gets all the way through the table and doesn't find a match it goes back to its counting routine and continues listening to the tapes.
Contemplating John's composition I'm led to imagine possible worlds where the activity of listening is very different from the normal ways which we have learned. p.11
Typed by Barb. Golden, Dec 4 1994