MUS 211 Study Guide F (Chapter 6)

Diatonic Seventh Chords

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  1. We have already studied the most common and the most useful of the diatonic seventh chords (major: ii7, V7, vii7; minor: ii7, V7, VII7, viio7).  Though appearances of the remaining chords as single sonorities are limited, all diatonic seventh chords are used freely and frequently in circle progressions (root movement down a 5th/up a 4th).
  1. Diatonic seventh chords in major:  I7, ii7, iii7, IV7, V7, vi7, vii7.
  1. Diatonic seventh chords in minor:  i7, ii7, III7, iv7, V7, VI7, vi7, VII7, viio7.
  • Minor:  In the ascending form, #6 produces (IV7 and) vi7 and #7 produces viio7, while in descending form, b6 and b7 produce VI7 and VII7.

The Major Seventh Chord

  1. The major seventh chord consists of a major triad and the interval of a major seventh between its root and its seventh.  The major-major seventh chord is usually referred to as simply a "major seventh" chord.
  • Diatonic major seventh chords in major:  I7, IV7.
  • Diatonic major seventh chords in minor:  III7, VI7.

Uses of Single Diatonic Seventh Chords

  1. Excluding the chords mentioned in Number 1 above, the sonority most commonly used non-sequentially is the subdominant seventh in its resolution to a chord of dominant function:  iv7-V, IV7-viio, or to the supertonic triad.
  1. The IV7 in a minor key has a dual function.  Not only can it resolve to the dominant, but it can also function as the secondary dominant chords V7/VII. E.g., in G minor: IV7 (C,E, G,Bb)-VII = V7/VII (C,E,G,Bb).
  1. The vi7 in a minor key, though uncommon, is useful anytime that a seventh chord appears above #6.
  • Most other single uses of these sonorities strongly suggest analysis of the seventh as the simple use of an ordinary nonharmonic tone.

Diatonic Seventh Chords in Sequence--Three Voices (5th omitted)

  1. In contrast to the scarcity of individual uses of these chords, their frequency in circle progressions is very high:
  • In major/minor keys, the sequence creates a chain suspension of sevenths alternating between the soprano and alto voices, each of which resolves to the third of the next seventh chord in the sequence.  (See p. 174 for illustration.)
  • In minor keys, descending melodic lines require the use of the descending form of the scale.
  • (When the bass line reaches 5-1 and a cadence occurs, the harmony is V7-i.  But if the sequence continues past that point, the harmony is v7-i.  The minor dominant seventh, v7, is rarely used elsewhere.)

Diatonic Seventh Chords in Succession and in Sequence--Four Voices

  1. In the case of dominant and supertonic seventh chords, when used succession with roots in the bass, one chord is complete and the next is incomplete (5th omitted, due to voiceleading).  The same is true for a succession or sequence of seventh chords in four voices, again, due to proper voiceleading.  (See p. 177 for illustration.)
  1. In inversion, seventh chords of any variety are usually complete due to the nature of the voiceleading.  (See p. 177 for illustration.)
  1. A sequence of diatonic seventh chords may be found with the seventh chords alternating with triads.

Writing Single Diatonic Seventh Chords

  1. The procedures already learned for the part-writing of seventh chords apply equally to the remaining seventh chords.  In four-voice nonsequential writing, all four voices are usually present, thereby avoiding any ambiguity of sound.  (E.g., does B,D,A represent B,D,F,A or B,D,F#A?)
  1. Only the subdominant seventh chord requires special treatment, caused by the fact that its root movement is usually up by step to V rather than down by a fifth as with most seventh chords.
  • This resolution can easily produce parallel fifths, but only when the chord's seventh is above its third. When the third is above the seventh, there is no problem.
  • To avoid parallel fifths, any other resolution not involving parallel octaves or augmented seconds is acceptable.  Usually, it is the third that moves unconventionally, down a fifth--an approach to the seventh of the following chord by leap from above. (See p. 187 for illustration.)

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