Harmonic literacy requires us to go beyond knowing the letter name and type of chords being played. We must also understanding how a chord functions in a particulate context.
To that end, a common practice for describing chords in functional harmonic terms is to analyze them using Roman Numerals.
The Roman Numeral naming convention works like this…
- Chords are named using the MAJOR SCALE as the point of reference.
- Each chord is assigned a number based on where the root of the chord falls along the scale degrees of the major scale. In the key of C, for example: C=1, D=2, E=3, F=4, G=5, A=6, B=7.
- Major chords use upper-case Roman Numerals.
- Minor chords use lower-case Roman Numerals.
- Diminished Chords use lower-case Roman Numerals with a “degrees” symbol (°) immediately following.
- Note: Other chord types are possible and will be discussed as they arise in context.
Here, for example, are all the diatonic (within the scale) Triads built from the C Major Scale named using Roman Numeral notation:
In major keys, the I chord establishes both the tonic note and major-ness of the key, while all of the other chords create unique tensions with respect to that key center.
And here are all the diatonic (within the scale) Triads built from the C Natural Minor Scale named using Roman Numeral notation. Notice that the major scale is still used as the point of reference:
In minor keys, the i chord establishes both the tonic note and minor-ness of the key, while all of the other chords create unique tensions with respect to that key center.
Of course, there are other tonalities besides major and natural minor: “Harmonic ” Minor, Mixolydian, Dorian, Blues, etc) … and there are many other kinds of chords (seventh chords, suspensions, etc) and chord functions (secondary dominants, pivot chords). It may seem like a lot know, but don’t despair. It is not as hard as you think. All you need right now is to understand the Roman Numeral naming conventions and to start thinking about chords in functional terms.