Sound Art Using Pre-Programmed Machines

Algorithmic Composition

Algorithmic composition has benefited greatly from computers. The earliest known use of computer to create a composition was in 1955 at the University of Illinois with Lejaren Hiller and Leonard Isaacson, where they created a notation score using a high-speed digital computer called Illiac with the piece Illiac Suite, that was then played by a string quartet.

The ILLIAC were a series of supercomputers built at the University of Illinois between 1951 and 1974.

The Illiac Suite is a composition for string quartet composed by a computer in 1957. The ILLIAC 1 computer generated a score for string quartet consisting of four movements. The first movement uses a cantus firmus (pre existing melody that forms the polyphonic composition). The second movement uses a four voice segment, the third is more focused on rhythm and dynamics, and the fourth uses different models of probabilities using Markov chains (stochastic model that describe the sequence)

Algorithmic composition can also use a system of rules, that determine what a computer can play or not play, as well as how to play. The algorithm imposes rules that will tailor the output of the program’s abilities to render a composition. Automated system’s like these were used by Kemal Ebcioglu (who worked with IBM) with the program CHORAL, that generated four part harmony chorales.

In fact, the CHORAL program harmonizes four part chorales in the Bach vein and contains 270 rules using a predicate calculus system that harmonizes a given melody. The 270 rules interpret the chorale by chord skeleton, melodic lines for each voice, and voice leading. These rules were using rigorous constraints that helped maintain a musical quality that also ruled out non acceptable solutions. CHORAL uses a programming language called BSL.

Another person that used this technique is William Shottstaedt with his “automatic species counterpoint program” that wrote music based on a counterpoint instruction book that focused on a style similar to the composer Palestrina. English composer Brian Eno used a program called Koan to make his album Generative Music, the program essentially outputs a series of sounds based on a the composer’s input values, or rules.

Automatic Species Counterpoint Program is a program that follows rules very closely. A penalty system is used to determine the degree of importance of a rule. If the penalty surpasses a certain amount, the path that was originally planned changes. To use examples, parallel fifths are 100% not allowed, a “very bad infraction” like direct motion to an octave has 200 of penalty, while repeated pattern of three notes has 4 as a penalty.

Generative Music:

Generative Music is simply music that changes constantly, and that is made by a system.