Irregular resolution

Irregular resolution Type I Playⓘ. Two common tones, two note moves by half step motion.
Irregular resolution through augmented sixth equivalence Playⓘ.[1] One common tone, three notes move by half step motion.

In music, an irregular resolution is resolution by a dominant seventh chord or diminished seventh chord to a chord other than the tonic. Regarding the dominant seventh, there are many irregular resolutions including to a chord with which it has tones in common or if the parts move only a whole or half step.[2] Consecutive fifths and octaves, augmented intervals, and false relations should still be avoided.[2] Voice leading may cause the seventh to ascend, to be prolonged into the next chord, or to be unresolved.[3]

The following resolutions to a chord with tones in common have been identified:

  • Type I, in which the root motion descends by minor third. C, E, G, B♭ would resolve to C♯, E, G, A; two tones are common, two voices move by half-step in contrary motion.
  • Type II, in which the root motion rises by minor third. C, E, G, B♭ would resolve to D♭, E♭, G, B♭; again, two tones are common, two voices move by half-step in contrary motion.
  • Type III, in which the root moves a tritone (two minor thirds) away. C, E, G, B♭ would resolve to C♯, E, F♯, B♭ = A♯; again, two tones are common (with enharmonic change), two voices move by half-step in contrary motion. This is called tritone substitution when the target chord replaces (or is inserted before) the original chord in a chord progression.
Regular resolution Playⓘ. One common tone, two notes moves by half step motion, and one note moves by whole step motion.

Type I is common from the 18th century; Type II may be found from the second quarter of the 19th century; Type III may be found from the mid-19th century. The composer Richard Edward Wilson is responsible for the categorization.

All three types describe a process of transforming a dominant seventh chord to a diminished seventh by raising the root by one semitone, then picking any other note in the chord and lowering it one semitone. That lowered note is now the root of a new dominant seventh chord. This works because diminished seventh chords are structurally equivalent in all of their inversions (a stack of minor thirds), so any note in a diminished seventh chord can be seen as the root note.

The most important irregular resolution is the deceptive cadence,[3] most commonly V7–vi in major or V7–VI in minor.[1][3] Irregular resolutions also include V7 becoming an augmented sixth [specifically a German sixth] through enharmonic equivalence[1] or in other words (and the adjacent image) resolving to the I chord in the key the augmented sixth chord (FACD♯) would be in (A) rather than the key the dominant seventh (FACE♭) would be in (B♭).

  1. ^ a b c Owen, Harold (2000). Music Theory Resource Book, p.132. ISBN 0-19-511539-2.
  2. ^ a b Chadwick, George Whitefield (2008). Harmony, a Course of Study, p.160. ISBN 0-559-22020-0.
  3. ^ a b c Foote, Arthur (2007). Modern Harmony in its Theory and Practice, p.93ff. ISBN 1-4067-3814-X.