398 / 18210 · Module 10 — Seventh Chords: The Language of Jazz, Pop, and Richer Harmony← prev⊞ allnext →
10.48Don't confuse chord quality and function
Important distinction:
C7 is a chord quality.
Its usual function depends on context.
In F major:
C7 = V7.
In C blues:
C7 may function as I7.
In other music it can have other roles.
So:
chord symbol describes the sonority; Roman numeral/context describes its function.
This distinction becomes increasingly important in jazz.