Musical canons
or rounds, existing from the late 15th century, can be considered a form of “algorithmic” music. A canon consists of a single melodic line that is written in such a way that the juxtaposition of it and delayed or even inverted versions of itself form a polyphonic work. Various rules are used in the creation of the melodic line in order to achieve results that conform to contrapuntal standard harmonic practices.
In a similar vein, 20th-century serialism practices made use of a system (or “algorithm”) for choosing the order of notes, rhythms and even dynamic markings, perhaps taken to its most extreme by Olivier Messiaen.
Where “rules” exist to help in the creation of music, computers can be programmed to follow those rules. One example includes Bill Schottstaedt's automatic species counterpoint program, which is based on the 18th-century counterpoint book Gradus ad Parnassum by Johann Joseph Fux.
Lejaren Hiller and Leonard Isaacson were the first to use a computer to create an original music score, the Iliac Suite, in 1957. Their approach involved having the computer generate and modifying musical materials, followed by selection of the best results using various rules.
Twentieth century minimalist works, such as Steve Reich's Piano Phase
and Philip Glass's Glassworks, lend themselves especially well to recreations using computers due to their significant use of repetitive materials.
