Fauxbourdon and Rule of the Octave in Music Theory

Fauxbourdon Techniques in Harmony

• A) Passing Interpolations

  These include:

  • Descending thirds progressions (IV6-ii6)
  • Descending fifths progressions (Haydn)
  • Sometimes descending fourths progressions (IV6-I6-ii6)

• B) Sorbet: Parallel First Inversion Triads

  In the key of G major, a passing connection from IV6 to I6 serves to break the cycle of recirculating harmonies. It's an extravagant way to connect IV6 to the ii6, but it leads to a normal cadence (ii6-I6/4-V-I). Make sure the parallel motion always leads to a recognizable destination (e.g., a strong dominant or a strong cadence). Think of fauxbourdon as a "thickened melody."

• C) I6 as a Neighbor to ii6

  Mozart's B-flat Piano Sonata ends with a ii6-I6-ii6-vii°6 progression. The I6 functions like a neighbor chord within a sequence of stepwise triads.

• D) Root Position Versions

  Sometimes parallel root position triads are used, such as in Mozart's E-flat Sonata (IV rising to I). Very common progressions include:

  • (IV-V-vi-vii°)
  • (I-ii-vii°-I)
  • (I-ii-vii°-I-IV-V)

• E) Four Voices

  Fauxbourdon works best in three voices to avoid parallel octaves or fifths. However, Bach's Chorale No. 106 (I-V6-IV6-iii6-ii6) leads to a modulation in F-sharp minor. Here, three voices move in parallel while the tenor moves back and forth between close and half-open chords.

Rule of the Octave and Scalar Bass Lines

• Ascending Scalar Bass Lines

  In C major, starting on low A: (I-vii°6-I6-ii6 or IV-V-iv or IV6-V6-I)

• Descending Scalar Bass Lines

  Starting on middle C:

  • (I-V6-IV6-V-V2-I6-vii°6-I)
  • Version 2 (root position dominant avoided): (I-V6-IV6-iii6-ii6-I6-vii°6-I)

• Variation 1: I6/4 for iii6

  • [I-V6-IV6-V6-I]
  • [I-V6-IV6-I6/4-ii6-cadence]

• Variation 2: IV for ii6 (Mozart)

  [I-V6-[IV6-I6/4-IV-I6]-vii°6-I]

  Bach's Fourth Brandenburg Concerto uses a close variant with iii6 instead of I6/4: [IV-I6-vii°6-I]. This is the Prinner progression, named by Robert Gjerdingen, and might follow I-V6-V7-I.

Common Harmonic Schemas and Patterns

These progressions function as "schemas," "outlines," or "background patterns":

• IV6-I6/4-(IV, ii6, or ii6/5)
• IV6-I6/4-IV-I6
• IV-I6-vii°6 ("Prinner")

Overlapping Progressions Example:

[I-V6-IV6-I6/4-IV/ii6-I6-vii°6-I]

• 1-3: Common opening
• 3-6: Common IV-I-IV-I pattern
• 3-5: Passing I6/4 progression
• 5-8: Prinner