A slide rule for music includes a first element that includes a first set of indicia representing in linear form the structures of a plurality of musical scales, chords and/or modes, and a second element that includes a second set of indicia representing the names of the notes of a chromatic scale. The second element is constructed and arranged for movement relative to the first element in two orthogonal directions, so as to indicate the relationship between the notes of the chromatic scale and the structure of a selected one of the musical scales, chords, and/or modes.