Editing Octatonic scale (section)

=== French sixth and Mystic chord ===
While [[Passing chord|used functionally]] as a pre-dominant chord in the classical period, late romantic composers saw the French sixth used as a dissonant and unstable chord. The chord can be built from the first, fourth, sixth and eighth degrees of the half-step/whole-step octatonic scale, and is transpositionally invariant about a tritone, a property somewhat contributing to its popularity. The octatonic collection contains two distinct French sixth chords a minor third apart, and since they share no notes, the scale can be thought of as the union of those two chords. For example, two French sixths based on G and E contain all the notes of an octatonic scale between them.

The octatonic scale is used very frequently for melodic material above a French sixth chord throughout the 19th and 20th centuries, particularly in Russia, in the music of Rimsky-Korsakov, Mussorgsky, Scriabin and Stravinsky, but also outside Russia in the works of Debussy and Ravel. Examples include Rimsky's ''Scheherezade'',<ref>{{Citation |title=Ears Wide Open Online {{!}} Deconstructing Rimsky-Korsakov's Scheherazade | date=15 June 2020 |url=https://www.youtube.com/watch?v=vRlnhaLEWMc |access-date=2023-08-19 |language=en}}</ref> Scriabin's ''Five Preludes, Op. 74'',<ref>{{Citation |title=Scriabin's Use Of The Octotonic Scale | date=20 March 2022 |url=https://www.youtube.com/watch?v=2zsmJ-XSlQI |access-date=2023-08-19 |language=en}}</ref> Debussy's ''Nuages'' and Ravel's ''[[Gaspard de la nuit|Scarbo]]''.<ref>{{Cite web |last=Ravel |first=Maurice |date=1908 |title=Gaspard de la nuit: III. Scarbo, piano score |url=https://imslp.hk/files/imglnks/euimg/2/22/IMSLP813748-PMLP2576-Gaspard_de_la_nuit_-_III._Scarbo.pdf }}</ref> All works are full of non-functional French sixths, and the octatonic scale is almost always the mode of choice.

By adding a major sixth above the root, from within the scale, and a major second, from outside the scale, the new chord is the Mystic chord found in some of Scriabin's late works. While no longer transpositionally invariant, Scriabin teases the tritone symmetry of the French sixth in his music by alternating transpositions of the Mystic chord a tritone apart, implying the notes of an octatonic scale.