Resolving the chordal seventh

The chordal seventh falls by step. Whatever chord carries it, the seventh is the tone that makes the chord restless, and its obligation is single: down one degree into the next harmony. The stricter styles also ask it to be prepared — sounded as a consonance in the same voice beforehand — and even where later practice strikes sevenths freely, the downward resolution never lapses. A seventh that rises, leaps, or simply vanishes leaves the progression’s tension unpaid.

Sevenths are how tonal harmony keeps moving, and the falling resolution is what chains chords into progressions: the seventh of V7 falls to the third of I, the seventh of ii7 falls to the third of V, and a whole circle-of-fifths sequence is nothing but this obligation honored link after link. Preparation is the style dial — strict counterpoint demands it, the galant relaxes it, but every idiom keeps the fall.

• Resolving the seventh upward, most often to double the root of the next chord, leaving the tension unpaid.
• Transferring the seventh to another voice at the change of chord instead of resolving it in its own line.
• Leaping away from the seventh to complete the next chord, repairing the harmony at the line’s expense.
• Striking an unprepared seventh in a strict-style context that expects the consonant preparation.
• Doubling the seventh, which puts the same unpayable debt in two voices at once.

• Jean-Philippe Rameau, Traité de l’harmonie réduite à ses principes naturels (1722), Book II, the seventh and its resolution — The seventh as the prototype of dissonance, its fall bound to the fundamental bass’s motion.
• Carl Philipp Emanuel Bach, Versuch über die wahre Art das Clavier zu spielen, Part II (1762), Part II, on the chords of the seventh and their resolution — The accompanist’s handling: preparation where the style asks, the fall always.
• Ebenezer Prout, Harmony: Its Theory and Practice (1889), The chapters on the dominant harmony — The classroom statement of the falling resolution into the third of the tonic.