Hexatonic scale

In music and music theory, a hexatonic scale is a scale with six pitches or notes per octave. Famous examples include the whole-tone scale, C D E F♯ G♯ A♯ C; the augmented scale, C D♯ E G A♭ B C; the Prometheus scale, C D E F♯ A B♭ C; and the blues scale, C E♭ F G♭ G B♭ C. A hexatonic scale can also be formed by stacking perfect fifths. This results in a diatonic scale with one note removed (for example, A C D E F G).

Whole-tone scale

The whole-tone scale is a series of whole tones. It has two non-enharmonically equivalent positions: C D E F♯ G♯ A♯ C and D♭ E♭ F G A B D♭. It is primarily associated with the French impressionist composer Claude Debussy, who used it in such pieces of his as Voiles and Le vent dans la plaine, both from his first book of piano Préludes.

This whole-tone scale has appeared occasionally and sporadically in jazz at least since Bix Beiderbecke's impressionistic piano piece In a Mist. Bop pianist Thelonious Monk often interpolated whole-tone scale flourishes into his improvisations and compositions.

Mode-based hexatonic scale

The major hexatonic scale is made from a major scale and removing the seventh note, e.g., C D E F G A C. It can also be made from superimposing mutually exclusive triads, e.g., C E G and D F A.

Similarly, the minor hexatonic scale is made from a minor scale by removing the sixth note, e.g., C D E♭ F G B♭ C.

Irish and Scottish and many other folk traditions use six-note scales. They can be easily described by the addition of two triads a tone apart, e.g., Am and G in "Shady Grove", or omitting the fourth or sixth from the seven-note diatonic scale.