1.1 Intervals
In 4-part harmony, we’ll consider 2 aspects of intervals: their type (melodic or harmonic), and their quality (consonant or dissonant). They will require a different treatment according to their type and quality.
Interval Types
There are two types of intervals:
- Melodic: Intervals played consecutively (i.e. a melody)
- Harmonic: Intervals played simultaneously (i.e. chords.)
In 4-part harmony, just like in species counterpoint, melodic and harmonic intervals will be treated differently and follow a slightly different set or rules.
When treating melodic intervals, we’ll be more interested in the melodic direction and making sure the line is easy to sing. On the other hand, when treating harmonic intervals, we’ll be interested in tonal fusion, chords, and voice-leading.
In 4-part harmony, we’ll be focusing more on harmony than in species counterpoint. Nonetheless, we’ll still want to consider the melodic aspect.
Interval Quality
Consonances
- There are two types of consonant intervals: perfect & imperfect.
- Perfect consonances tend to sound ’empty’, so we’ll try to hide them.
- Imperfect intervals sound more ’rich‘.
| Perfect Consonances | Imperfect Consonances |
|---|---|
| Perfect Octaves (P8) | Major Thirds (M3) |
| Perfect Unisons (P1) | Minor Thirds (m3) |
| Perfect Fourths (P4) | Major Sixths (M6) |
| Perfect Fifths (P5) | Minor Sixths (m6) |
The perfect fourth is generally considered like a consonance, except when forming an interval with the bass line, in which case it will be considered dissonant. (see more with second inversions)
Dissonances
Other intervals are considered dissonant, some of which are considered “soft” and some of which are considered “hard”
| Soft Dissonances | Hard Dissonances |
|---|---|
| Major Seconds (M2) | Minor Seconds (m2) |
| Perfect Fourth (P4) | Major Sevenths (M7) |
| Minor Sevenths (m7) | Minor Ninths (m9) |
| Major Ninth (M9) |
Other augmented and diminished intervals are considered “soft”
The triton (d5 or A4) is generally considered like a soft dissonance in the context of tonality, although in some other musical contexts, it could be considered a consonance. In 4-part harmony, we’ll be treating it like a dissonance.
Enharmonic Intervals
Enharmonic intervals are intervals which sound identical, but are spelled differently. Even though they sound the same, they don’t occupy the same musical function.
A note with a sharp will tend to resolve upward, while a note with a flat tends to resolve downward.
One of the most important intervals we’ll come accross is the augmented second (present in the minor harmonic scale), which sounds identical to a minor third, but which appears in specific contexts.