Roman Numerals and Harmonic Functions
Harmonic Functions and Progressions
Lead Sheet symbols name the chords in a song, but Roman Numerals are used to identify their harmonic function and relationships. Each chord in a major or minor key is built on a scale degree, and the quality of these chords are replicated in every key. These are the scale degrees:
How Chords Progress
There are three basic PROGRESSIONS. (Other movements are RETROGRESSIONS.)
- Down a 5th
- Up a 2nd
- Down a 3rd
In describing root movement by intervals, we will consistently refer to the downward 5th, which lands on the same pitch as the upward 4th, but there is no reason to call this movement by two different names. Likewise, a 3rd down is equal to its inversion, a 6th up.
In addition to these three basic movements, a chord may progress to the tonic (I) or dominant (V) at any time. Thus, the vi – V movement is common, as is the ii – I movement. Both are considered retrogressions. The leading tone 7th (viiº) typically moves to the tonic (I).
Chords can be grouped into three basic families. These are the Subdominant, the Dominant, the Tonic. The Subdominant if often called the Predominant. They tend to move in this fashion:
Either of the two chords in each family may be used, and progressions follow the root movements described earlier. For example, consider the root movements in this progression:
The movement is down a 3rd, down a 3rd, up a 2nd, and down a 5th.
Diatonic Chords in Major and Minor Keys
Major:
Minor:
(Harmonic form is commonly used as an abstraction)
In tonal music, the Melodic Minor form is always used. This means that any ascending line uses the raised 6th and 7th scale degree when approaching the tonic. Conversely, any descending line uses the lowered, or natural minor form of the 7th and 6th scales degrees when approaching the 5th. It could be expressed this way: 
These chromatic alterations could be a sharp, natural, or flat depending on the key signature. We consider these altered notes to be part of the minor key, and these inflections add variety compared to just seven tones in a major key. They also introduce additional chords that are not contained in the Harmonic Minor scale.
Commonly used chords in Minor keys: ii, IV, v, VII (Subtonic),
Other possibilities that are rarely used include: III+ and viº
Activities
- Memorize and name the diatonic triads and seventh chords on each scale degree in any key.
- Play the diatonic triads and seventh chords through 4 sharps and flats on a piano or guitar.
- Outline these triads with your voice, using solfege syllables.
- Play the Melodic Minor scales through 4 sharps and flats on a piano or other instrument.
Music Courseware Activities
Visitors – Select the Activity Written: Scale Type
Visitors – Select the Activity Aural: Scale Type
Visitors – Select the Activity Written: Diatonic Triads
Visitors – Select the Activity Aural: Harmonic Function
Students – Take a test or quiz assigned by your instructor.