MusicReasonResource
Chord Function, Cadence, and Substitution
Harmonic function is contextual evidence from tonal center, sequence, and resolution, not a permanent tag stapled to a chord.
MusicReasonResourceChord Function, Cadence, and Substitution
A chord symbol names notes. A Roman numeral names a function: the role that chord plays in relation to a tonal center at a specific moment. The same G major chord is a I chord in G major and a dominant V chord in C major; nothing about the notes changes, only the context around them does.
Three functional families, one worked example
| Chord | Roman numeral | Function |
|---|---|---|
| D minor | ii | Predominant, leans toward the dominant |
| G major | V | Dominant, creates tension that pulls toward the tonic |
| C major | I | Tonic, the point of harmonic rest |
Roman Numeral Analyzer and Chord Function Analyzer both assign this kind of label relative to a stated (or inferred) tonal center, never from a chord symbol read in isolation.
An applied dominant borrows tension, briefly
A chord like D7 resolving to G within a passage in C major is acting as V/V, "the dominant of the dominant": it temporarily borrows the pull a dominant has, aimed at a scale degree other than the main tonic, without actually changing key. Secondary Dominant Finder identifies exactly this kind of brief tonicization and distinguishes it from an actual modulation.
A cadence is a functional pattern, not a chord pair
"Authentic," "half," "plagal," and "deceptive" name specific functional resolutions (or deliberate non-resolutions), not just any two chords in a row. Cadence Finder looks at the functional relationship between consecutive chords to classify which cadence family, if any, is present.
A substitution has to earn its place, not just sound close
Chord Substitution Finder proposes a replacement chord only when it can state the specific rationale: shared function, shared voice-leading tones, or a tritone relationship, for example, rather than an unexplained "chords that sound similar" list. Modal Interchange Explorer and Reharmonization Explorer extend this into borrowing chords from a parallel mode and building fuller alternate harmonizations.
Frequently asked questions
Yes. Function comes from a chord's relationship to the tonal center and how it resolves in that specific passage, not from the chord symbol alone. A G major chord is dominant in C major and subdominant-adjacent (bVII-style) borrowed color in G minor.
Chord Substitution Finder only proposes a replacement that preserves the original chord's functional role or shares enough voice-leading and tone content to serve the same resolution, stated with its specific rationale, not a generic "chords that sound similar" list.
Not by itself. A secondary dominant briefly tonicizes another scale degree without abandoning the original key; Modulation Planner and Secondary Dominant Finder handle these as distinct, related questions rather than treating one as a synonym for the other.