As a Classical reading, the piece is a study in making a ground bass generate architecture. The opening passacaglia does not present recurrence as background support. It makes recurrence the central discipline: a fixed tread that can carry changing harmony, register, density, and contrapuntal pressure.

The early variations show Bach's formal severity. Around 0:08-2:30, the bass ground stays legible while the upper voices test different weights above it. The technique is not display for its own sake. It lets the listener hear how much change can happen without abandoning the frame.

By the middle and later passacaglia, the variation principle has become structural force. The organ's sustained body turns each return into a load-bearing event, and the increasing density makes the ground feel less like a theme than a condition. That is why the fugue can enter around 7:30 without sounding like a separate piece.

The fugue transforms the passacaglia's law into counterpoint. Instead of one ground supporting variations, the subject and answering voices distribute the old compulsion across the whole texture. Pursuit, imitation, and register change become the new way recurrence moves.

The final minutes close the classical argument by gathering variation and fugue into one authority. The organ does not simply get louder or faster; it makes the accumulated order feel inevitable. When the terminal silence arrives after about 12:35, the form has completed itself by making recurrence audible as memory.