ABSTRACT
In Experimental Musical Instruments' February 1989 issue, the authors published a sound spectrum chart, laying out values for frequency, pitch name, and wavelength, over the entire audible range. Tunings from diverse music cultures, historical European scale systems, and scales created by contemporary composers and theorists are represented on the chart. To help demarcate the tonal territory, horizontal reference lines cross the entire chart at heights corresponding to certain basic just intervals: the major second 9:8, the major third 5:4, the perfect fourth 4:3, the perfect fifth 3:2, and the major 6th 5:3. The ratios appearing on the chart give the frequency of the given scale degree over the frequency of the starting tone of the tuning, reduced to the simplest terms. On the chart, the blue tonalities appear, inevitably, primarily as a series of gradations.
