Secondary Dominant (V of vi) I-III7-vi-IV
Piano sound loads on first tap. Resolved in the key of C — every chord links to its full analysis.
A textbook tonicization: raising the mediant to a DOMINANT 7th (III7) makes it act as the 'V of vi', pulling with borrowed tension into the relative minor before the subdominant (IV) rejoins the diatonic path.
What each degree does
Feels like home — complete rest, where the piece departs from and returns to. The major tonic, where everything settles.
The V OF vi — an applied dominant tonicising the relative minor. A major III with a 7th resolving to vi.
The relative minor — the tonic's reflective shadow. It often replaces I in a deceptive cadence, where you expected home and its sad side arrives instead.
A step out from home into the light — the subdominant. It sets up the dominant or resolves with a plagal ('amen') colour, opening space without sharp tension.