This article summarizes recent investigations into the psychological representation of pitch relations in tonal music. Evidence is found for the internalization of tonal structure at three levels of organization: musical tones, chords, and keys. Each level contains a well-articulated pattern of interelement associations, and strong interlevel dependencies are identified. A quantitative account of the hierarchy of stability that applies to the set of musical tones and chords is provided. Structure at these levels is found to depend on the context in which the musical elements are embedded. Thus, tones and chords are interpreted in terms of their functions in a system of musical keys, whose interrelations are represented by a regular spatial configuration derived from empirical data. The influence of this system of knowledge on the encoding, interpretation, and remembering of music is described. These results suggest that the listener relates the sounded elements to an abstract internal representation of the structural regularities underlying tonal music.