Thus far, we have focused on the building blocks for constructing music such as pitches, intervals, chords, and melodic interaction, but we have yet to look at how these elements combine to create harmony. To study harmony, we need a tool that describes chords and sonorities based on their function rather than their components.
To this point, we have used leadsheet notation to convey the essential components of a chord: root, bass note, quality, inversion, and any additional pitches. But a single leadsheet chord does not provide context about its role in the music.
Cmin7/E-flat
From this, we know that the chord has the pitches C, E-flat, G, and B-flat with the E-flat as the lowest voice, but we do not know how it relates to the chords around it. Is it stable, and does it sound final? Or is it unstable and pulling toward a different chord?
When music theorists want to discuss diatonic (key-based) function, we label chords using a Roman numeral system based on the chord’s position within a particular key.
Using the examples below, determine:
Note that the ABC notation used in these examples has limitations on what kind of text can be entered. In the Roman numeral system, everything other than the Roman numeral itself should be written as superscript.
You may already be familiar with the basics of using Roman numerals for labeling diatonic chords, but it is helpful to have a complete breakdown of the system into its fundamental components.
ti
(raised seventh scale degree), and this is considered the diatonic function. The naturally-occurring VII chord is used much less and has a more limited scope in common practice.Chordal fifth - The chordal fifth is altered by adding either a o (the diminished symbol) for lowered fifths or a + for raised fifths.
Remember that when you add an inversion to a seventh chord, you do not need a 7 anymore. The inversion implies the seventh.
By having each part of a Roman numeral describe an isolated chord tone, we are able to accurately describe any chord that can occur in our tonal harmony system, regardless of whether it has a standard function.
Chordal member | Default implied pitch | To raise by semitone from default | To lower by semitone from default |
---|---|---|---|
root | diatonic scale degree | sharp symbol in front of Roman numeral* | flat symbol in front of Roman numeral* |
third | based on case of Roman numeral | upper case (M3) | lower case (m3) |
fifth | P5 above root | + after Rom num | o after Rom num |
seventh | m7 above root | M before inversion figure | o before inversion figure** |
*For clarity’s sake, we always use a sharp or flat symbol to show that we are raising or lowering the root, even if you are actually adding a natural. When analyzing pieces that change keys–especially to distant keys–this makes it much easier to look for similar patterns, regardless of whether the key signature uses sharps or flats.
**Because the diminished symbol o implies the interval of a d5 AND a d7, you must use the half-diminished symbol if you wish to alter the fifth but leave the chordal seventh as a m7 above the root.
There are two more possible additions for Roman numerals, but these are advanced techniques are will not be necessary until Unit 19. For completeness, we will discuss them here, but if you would rather skip this for now, please do so.
The word add is used when a tone is a functional part of the chord but does not belong to a standard triad or seventh chord. A good example of this would be a triad that has a functional 9th above the root. For example, in C major, if a C major triad were to have a D as necessary to the function of that chord, it would be labeled Iadd 9. This clearly identifies the triad plus the additional ninth, but it also omits the chordal seventh. If it were a major seventh chord, you would not need use the add function, because a 9 would imply everything below it. So a IM9 is assumed to have 9th, 7th, 5th, and 3rd above the root.
The word sub is used when a tone replaces another chord tone. The replaced chord tone is always the closest chord tone below the subbed chord tone. For example, if the tonic triad in C major had a 4th above the root instead of the chordal third, you would label that as Isub4. This implies that the 4th replaces the chord tone directly below it, so this would be a triad with C, F, and G.