Lecture by Prof. David Temperley, PhD: Information Flow in Music

Describing the music of Palestrina, the musicologist Knud Jeppesen wrote: “It avoids strong, unduly sharp accents and extreme contrast of every kind and expresses itself always in a characteristically smooth and pleasing manner.” What is it that makes Palestrina’s music seem “smooth”? I will argue that Jeppesen in this quote is recognizing an important principle that applies not only to Palestrina but also to many other musical styles: the principle of Uniform Information Density (UID). Information, in the mathematical sense, is inversely related to probability: Events that are low in probability are high in information. The principle of UID, which was first observed in research on language, states that communication is optimal when information flows at a fairly uniform, moderate, rate. Applied to music, the UID principle suggests that high-information (low-probability) events should be lengthened and spaced out in time, and that events that are low-probability in one respect should be high-probability in other respects. I will discuss applications of the UID principle in several diverse areas of music: rules of Renaissance counterpoint, the construction of classical themes, and patterns of expressive performance.