Abstract Musical Scales are said to be Harmonic or Non-harmonic according as they are or are not adapted for playing in harmony. Most accounts of non-harmonic scales, such as the Greek, Arabic, and Persian, either (1) are derived from native theoreticians, who give the comparative lengths of the strings for the several notes, whence, on the assumption that the numbers of vibrations are inversely proportional to the lengths (which is only approximately correct in practice), the intervals from note to note are inferred; or (2) are attempts to express the effects of the intervals by the European equally tempered scale. The former when reduced, as in Professor J. P. N. Land’s “Gamme Arabe,” 1884, is the best that can be done without hearing the scales themselves. The latter is utterly delusive and misleading.