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Paper Summaries!!


Paper summer 1: Alpern, Adam. Techniques for Algorithmic Composition of Music. 1995.

Alpern discusses three approaches to composition.

The first is accomplished using his program Contour, which he wrote in Common Lisp. Contour does a very basic musical analysis of a piece, and then expands the piece based on that analysis. The analysis consists of labeling if notes are rising or falling to determine the “contour” (rising or falling) of a phrase or piece. At this point, Contour uses each note of the original melody as a starting point of a new melody which must be characterized by the same contour as the original. Lastly, Contour appends all the new melody fragments together. Contour works well in combination with using 1/f noise to generate the new melodies. On its own, 1/f noise tends to be to wandering and random to be pleasing, but applying Alpern's Contour program gives more structure to the result.

Alpern also explores using Nonlinear Dynamical Systems and Chaos in composition. He specifically focused on Henon Maps and Logistic Map. To use these equations in composition, they are evaluated iteratively, by calculating a solution and using that solution as input values for the next iteration. Using chaos to compose produces interesting results because as the equations are evaluated iteratively the solutions will be similar but not the same due to the properties of attractors.

The last approach Alpern considers is genetic programming. Alpern identifies the weakest point of genetic composition is the “Computational Critic” (the fitness test). Alpern's solution is to use several independent tests which critique different aspects of melodies and rate them by comparing them to a “case-base” of melodies imputed by the user. The Critic tests “Tonal-novelty-balance,” “Rythmic-novelty-balance,” “Tonal-response-balance,” “Skip-balance,” and “Rhythmic-Coherence.”

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