Music is a physically measurable phenomenon moving through time. It is universal to humanity: the tendency to make music is right there in our nervous systems with our propensity for speech, so it provides material for the assessment of all societies and ages.

If we want to investigate medieval and Renaissance Europeans' sense of time as a part of their perception of reality, we can hardly do better than to examine their music. They, like the ancient Greeks, believed that it was an emanation of the basic structure of reality, even part of that structure. “Without music,” wrote St. Isidore of Seville, the Middle Ages' favorite encyclopedist, “there can be no perfect knowledge, for there is nothing without it. For even the universe is said to have been put together with a certain harmony of sounds, and the very heavens revolve under the guidance of harmony.”