(musicTheory2) Lecture Notes: Ch. 19, other seventh chords

The subdominant seventh (IV7 and iv7):

  • another choice to harmonize scale-degree 3-2-1 descents at cadences, but unlike the cadential 6-4 can be on a strong or weak beat.
    • The third of the iv7 must leap down to double the fifth of the V chord to avoid parallel fifths.
  • can be part of V – IV6-5 – V6-5 – I progression (scale degrees 5 – 6 – 7 – 8 in bass).
  • IV4-2 can go to ii7 or vii°6

Tonic seventh (I7 and i7):

  • destabilizes tonic (can’t be used as target chord of cadence)
  • often sets up a descending circle of fifths sequence.
  • I – I6-5 – IV (I6-5 instead of I6)
  • I – I4-2 – IV6 (bass descends 1 – 7 – 6; leading in bass does not resolve)

Other diatonic sevenths usually occur as part of a melodic/harmonic sequence.


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