To this point in the course, we have focused on essential elements – the building blocks for constructing music – such as pitches, intervals, chords, and melodic interaction. But we have not looked 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.