The double cadence

The long form of the authentic close: the bass takes the dominant and holds it while the upper voices pass through four stations — the plain dominant, the six-four, the suspended fourth, and its resolution to the third — before the fall to the tonic. The double cadence is the thoroughbass player’s signal that a real ending has arrived: it spends a full measure or more announcing the close, and its 4–3 tail is the compound cadence embedded at the end of the longer ritual.

Reserved for the closes that matter most — the end of a large section, a movement, or an entire work — where a plain V–I would pass too quickly for the weight of what has come before. A continuo player hearing the bass settle onto the dominant and cycle through its four stations knew a real ending was underway, and could shape the ensemble’s final gesture accordingly. Because it absorbs the compound cadence as its own closing gesture, the double cadence reads as an amplification of the ordinary close rather than a different device.

• Letting the bass leave the dominant before all four stations have passed, which collapses the ceremony into an ordinary compound cadence.
• Skipping the six-four station and moving straight from the plain dominant to the suspended fourth, producing the shorter formula while claiming the longer one’s name.
• Leaving the suspended fourth unprepared as a consonance in the six-four that precedes it.
• Resolving the suspended fourth by leap instead of stepping down to the third.
• Doubling the leading tone in the final approach to the tonic.

• Fedele Fenaroli, Regole musicali per i principianti di cembalo (1775), The rules of the cadences (the double cadence) — The highest grade of the Neapolitan closes: the dominant prolonged through its stations.