Composing Music with Computers (review)

Eduardo Reck Miranda's new book, Composing Music with Computers, is an indispensable contribution to the scarce literature on algorithmic composition. In algorithmic composition, composers use formal processes to generate musical material, forms, or even entire pieces. Composing Music with Computers focuses on generative processes, those that formulate output from the operation of mathematical functions rather than from the manipulation or transformation of existing musical material.

Early on, the author identifies abstraction boundaries between the microscopic level, the note level, and the building-block level. The microscopic level is basically that of sound synthesis; the note level is traditionally represented by notation in a score; and the building-block level is a higher, formal abstraction combining and arranging sequences of notes. The processes described in the text can be applied to any of these levels, but for the purposes of discussion, the book focuses primarily on the note level.

Mr. Reck Miranda is certainly well placed to write this study: he has extensive experience as both a composer and a programmer of large-scale artificial intelligence systems. Moreover, he makes cogent use of cognitive arguments to characterize the nature of the composer's craft. The scope of the discussion, then, is daunting: from general principles of music composition through the cognition of composers and listeners to the algorithmic techniques of generating musical materials and form. Given that scope, the book is relevant to several different audiences. Of those audiences, including computer scientists, mathematicians, and researchers in artificial intelligence, the book is addressed most directly to composers.

For example, the second chapter, "Preparing the Ground," leads the reader through some fundamentals of discrete mathematics, set theory, logic, matrices, formal grammars, probability, and computer programming. This material would be familiar territory to those with a technical background, but is very clearly explained and demonstrated for the benefit of those with more purely musical training. Brief introductions to serialism and formalized music follow that fill the opposite role: informing those with more technical training than musical.

Subsequent chapters extend the introductory material and relate it to compositional applications. Chapter 3 is devoted to probabilities, grammars, and automata. Building on the foundation of chapter 2, the reader is shown applications of random distributions, Markov chains, and so on, to music generation. Similarly, chapters 4, 5, and 6 cover iterative algorithms, neural computation, and evolutionary music, respectively.

In my experience, the greatest difficulty for students trying to compose algorithmically is not learning the procedures—it lies in imagining how the procedures might be used to produce their own music. Mr. Reck Miranda points to this issue himself when discussing the musical applications of iterative processes:

However, finding an effective method for mapping the orbits [of an iterative process] onto musical parameters is not an easy task. This is one of the greatest difficulties composers face when working with algorithmic composition systems that use the output from essentially non-musical processes; that is, non-musical in the sense that they were not originally developed with a musical perspective in mind.

Some composers simply never will have a need to compose procedurally, no matter which tools they have, and others will see immediately how to employ algorithms in their work. For those in the middle, Composing Music with Computers is an essential guide. That said, the book may have been even more valuable to such readers with a greater range of worked-out examples. Throughout the body of the text, there are helpful illustrations with musical material provided at every appropriate juncture. These illustrations tend to be short and didactic, however, rather than elaborated and evocative.

The most useful bridge between theory and practice is provided by chapter 7, a group of three...