(Note: Midi files of many of the examples are included at this site. To learn how to play these files on your machine, go to Midi Setup.)An octatonic scale consists of alternating whole and half steps. It is an eight-tone scale; that is, eight tones are required to fill in the octave. According to McHose, the octatonic scale was first used by Rimski-Korsakov. His student, Igor Stravinsky used it extensively, especially in the Rite of Spring.
The octatonic scale has only two modes. As shown in the next two examples, Mode 1 begins with a whole step and Mode 2 begins with a half step. Mode 1 consists of two minor tetrachords, the second starting at the tritone.
Example 1: Octatonic Mode 1
Mode 2 consists of two diminished tetrachords, the second starting at the tritone.
Example 2: Octatonic Mode 2
The tetrachords shown above recur often within each mode. For example, the minor tetrachord appears on steps 2, 4, 6 and 8 of mode 2. The diminished tetrachord appears on steps 2, 4, 6 and 8 of mode 1. Bartok's Mikrokosmo 101, Diminished Fifths, is based on the polyphonic interplay of the two Mode 1 tetrachords at the tritone.
Debussy based the Nuages ostinato on the diminished tetrachord of Mode 2.
Mode 2, also called the "half-step diminished scale," is used in Jazz improvisation in association with diminished seventh chords.
Though not as extreme as the whole tone scale, pattern redundancy in the octatonic scale creates invariant features. For example, a minor third, a tritone, a diminished triad or a diminished seventh chord can be built above every step of the scale.
Patterns built on bottom note of the whole step or the half step recur on alternating steps. Thus, the chord types shown in Example 3 occur on steps 1, 3, 5 and 7 of Mode 1 (or steps 2, 4, 6 and 8 of Mode 2). Note the polychord made of two diminished seventh chords.
Example 3: Chords on Steps 1, 3, 5 and
7 of Mode 1
Example 4: Chords on Steps 1, 3, 5 and 7 of Mode 2
The recurring or redundant features discussed above tend to limit how long octatonic passages can be used to sustain interest. On the other hand, an octatonic passage adds fresh harmonies and stresses that give relief to more conventional materials. It can be used to good poetic effect.
Because minor thirds and tritones recur so frequently, octatonic passages always carry the tint of the tritone. Moreover, the underlying harmonies of octatonic passages tend toward tritone bearing chords, especially the hues of altered dominant and leading tone chords.
Example 5: Repeating Figures
Example 6: Ostinato
Example 7: Shallow Contrary Contours
Example 8: Mirror Lines
Example 9: Homophonic Texture
Example 10: Complex Chords in Homophonic Texture
Example 11: Interaction of Two Mode 2 Tetrachords
Example 12: Mirror Imitation
(My apologies for the two temporal "hicoughs" in example 12. It plays back the same way in my scoring program, Overture. Any suggestion will be greatly appreciated.)
An E-E flat ostinato is embedded in the following accompaniment. The chords implied by the interaction of melody and accompaniment are ambiguous. The chords could be a C7(flat 5, flat9, sharp 9) or a Cmi7 (flat 5, flat 9), both with an added 6th -- or an alternation between the two colors.
Example 13: Ambiguous Harmonies