Like Grainger in England, Bartok brought with him an Edison cylinder, and he listened as the machine listened. He observed the flexible tempo of sung phrases, how they would accelerate in ornamental passages and taper off at the end. He saw how phrases were seldom symmetrical in shape, how a beat or two might be added or subtracted. He savored “bent” notes – shakings above or below the given now –and “wrong” notes that added flavor and bite. He understood how decorative figures could evolve into fresh themes, how common rhythms, tied disparate themes together, how songs moved in circles instead of going from point A to point B. Yet he also realized that folk musicians could play in absolutely strict tempo when the occasion demanded it. He came to understand rural music as a kind of archaic avant-garde, through which he could defy all banality and convention.
–Alex Ross, The Rest Is Noise, p. 83