Because of its temporal nature, music presents a unique challenge to the perceptual systems. To understand music one must infer underlying musical structure based on a musical surface that is constantly changing. Accordingly, a central component of musical behavior involves the abstraction of underlying musical structure from the musical surface. The following paper discusses the central importance of such abstraction, looking at examples of the role of abstraction based on a variety of underlying representational structures (tonal hierarchies, tonal-metric hierarchies, melodic patterns). These examples support the idea that musical understanding is fundamentally driven by the apprehension of structural patterns, and not by auditory surface information.