MUS 211 Study Guide C (Chapter 3)

Modulation with Diminished Seventh Chords

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  1. As a pivot chord, the o7 is more versatile than any other chord that could be used for this purpose.

  1. Any o7 can follow a given chord in the original key and then become a useable function in any other key.

  1. The following characteristics of the o7 chord allow this versatility:

  • When inverted, its sound is the same as any other position of the chord,

  • Any o7 chord, and each of its inversions, can be spelled enharmonically.

  1. Do not use a flatted tone as a root, except Bb (gCb).

Using the o7 as a Pivot Chord

  1. Most often, the o7 pivot is spelled in the new key only.  Some composers, however, may spell it in both keys (enharmonically), utilizing two chords, of course.

The Secondary Leading Tone Chord as a Pivot in the New Key

  1. A common use of the o7 pivot as a secondary leading tone seventh chord is to use a chord spelling which is common to both keys.

  • Example:  In the key of D Major, o7/ii is spelled D#, F#, A, C. If modulating to the key of A Major, the same spelling would then become o7/V in the new key.

The Nondominant Diminished Seventh Chord as a Pivot

  1. The two nondominant diminished seventh chords, #iio7 (6I6) and #vio7 (6V6 or V six-five), are also useful as a pivot in either or both of the two keys of the modulation.

Alternate Spellings of Diminished Seventh Chords

  1. Any diminished seventh chord may at times be found with a spelling not in accordance with its function in its particular key.  Usually, the reason is due to its particular function in one of the two keys, sometimes having to do with simplicity of notation.

Modulation by Resolving Early One Member of a o7 Chord

  1. When any member of a o7 chord is lowered one half step, that lowered tone becomes the root of a major-minor (dominant quality) seventh chord, which facilitates a modulation.
  • Lowering members of the o7 chord (B, D, F, Ab) by one half step:
Member lowered: to: Resulting M-m 7th:
Root - B Bb Bb D F Ab
Root - B A# A# Cx E# G#
Third - D Db Db F Ab Cb
Third - D C# C# E# G# B
Fifth - F E E G# B D
Seventh - Ab G G B D F

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