Abstract: Isochords is a visualization of music that aids in the classification of musical structure. The Isochords visualization highlights the consonant intervals between notes and common chords in music. It conveys information about interval quality, chord quality, and the chord progression synchronously during playback of digital music. Isochords offers listeners a means to grasp the underlying structure of music that, without extensive training, would otherwise remain unobserved or unnoticed. In this paper we present the theory of the Isochords structure, the visualization, and comments from novice and experienced users.