(musTh1) Diatonic Harmony

Using Roman Numerals to Label Harmonies

We’re moving away from using commercial chord symbols to label harmonies. From now on, we’ll be using Roman numerals to label harmonies within a key. (diatonic harmonies)

  • The scale degree of the root is the Roman numeral you use to label.
  • Uppercase and lowercase (with superscript) denotes quality. Uppercase equals major triad. Lowercase equals minor triad. Lowercase with a ° equals diminished triad. Uppercase with a + equals an augmented triad.
  • Inversions of chords are shown with figured bass symbols (without alterations).

Harmonic Function and Harmonic Tendency

These two concepts are related. Harmonic function describes the way chords relate to one another. It uses names based on the scale degree of the root, but with chords grouped into a limited number of functions.

  • I has a tonic function. (T)
  • V and vii° have a dominant function. (D)
  • ii and IV (ii° and iv) have a pre-dominant function. (PD)
  • iii and vi (III and VI) have a variable function. (V)

Knowing the function of a harmony gives us information about the harmonic tendency of a chord.

  • Dominant function harmonies tend to move to tonic function harmonies. So V and vii° tend to move to I
  • Pre-dominant function harmonies tend to move to dominant function harmonies. ii and IV tend to move to V and/or vii°
  • Variable function harmonies have no strong tendency. They can move to a variety of harmonic functions. (VII in minor falls into this category as well.)

Harmonic function is guided by two over-riding tendencies: the cycle of fifths (descending) and harmonic sequences.

  • A typical cycle of fifths progression would be iii – vi – ii – V – I, where the root of each successive harmony is a fifth below the preceding harmony. A cycle of fifth progression could use only a part of this pattern.
  • Harmonic sequences tend to follow melodic sequences. Melodic sequences are a series of intervals presented on different scale degrees. The strength of the melodic sequence guides harmonic tendencies in ways that do not follow either a cycle of fifths or the functional tendencies described above.


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