Musical scores are often annotated with harmonic information, but text-based methods are not visually preattentive, and existing glyphs rarely capture the frequency of chordal changes or their harmonic function. Furthermore, although color is ideal for representing categorical variables, there is not yet a consistent set of colors in use for the 12 pitch classes and the 24 keys of Western tonal music. This case study addresses both of these gaps through novel applications of shape and color theory.

A custom three-dimensional model of preattentive space (sharp vs. smooth, segmented vs. not segmented, compact vs. open) informs the design of compact glyphs which embody a chord's modal brightness (Major vs. Minor). And twelve familiar, easily identifiable, and consistent colors are mapped to specific keys to create robust 12- and 24-color ordinal categorical palettes. Combined or individually, these provide new and effective communication tools for general use in visualization.