Two mutually exclusive whole-tone scales are formed by choosing alternate notes of the chromatic scale (which has 12 notes per octave). Thus, the whole-tone scale comprises six degrees per octave. Because there are no semitones, all thirds are major, and thus all triads (triad) are augmented. Whole-tone harmony, with its similarly structured chords and absence of semitones, lacks the harmonic contrasts and resolutions of the major-minor system and its different keys; with whole-tone harmony, the sense of key centre depends instead on repetition and melodic emphasis. In Western art music, the whole-tone scale is associated with the decline of functional harmony in the late 19th century.

The first composers to begin experimenting with the chromatic alterations that imply whole-tone harmony within a generally tonal framework were Franz Liszt (Liszt, Franz) and Russian composers such as Mikhail Glinka (Glinka, Mikhail), Modest Mussorgsky (Mussorgsky, Modest), and Aleksandr Borodin (Borodin, Aleksandr); these were followed in the early 20th century by the more attenuated tonal experiments of Anatoly Lyadov (Lyadov, Anatoly), Aleksandr Scriabin (Scriabin, Aleksandr), and Vladimir Rebikov. Whole-tone patterning, with no leading tones or dominant harmony, became a distinctive aspect of the music of the French composers Claude Debussy (Debussy, Claude), Paul Dukas (Dukas, Paul), and others at the turn of the 20th century. Whole-tone harmony thus became a means of suspending or dissolving the perception of tonality in music of this period. Some outstanding examples incorporating extensive whole-tone harmony are Debussy's "Voiles" (1909; Préludes, Book 1, No. 2) and "Cloches à travers les feuilles" (1907; Images, 2nd series, No. 1), as well as Dukas's opera Ariane et Barbe-Bleue (1907).