During his last years, Bach explored the limits of contrapuntal possibilities. As a contribution to the Leipzig music scholar circle "Mizler'sche Sozietät" he presented in 1748 five "Canonical Changes" on "Vom Himmel hoch," which he revised just before his death by changing the original row and put the third movement now to the end: The result was a new central symmetry instead of an order of enhancement before.
In the first two trio settings, two manual parts are playing an octave canon respectively quint canon above the quit pedal melody line. The third movement reflects in two upper voices each part of the melody line over a free bass and changes by voice exchange from the sixth to the third canon. Two sub-voices repeat this structure as second or none canon, complemented by a virtuoso soprano line. In the most effective final enhancement ("Stretta") the melody lines are heard simultaneously in different tempi. The fourth canon ("cantabile") consists of two sub-voices in the seventh-pitch; a free alto accompanies the soprano cantus firmus, composed in quiet halves. The last variation carries out the octave canon by harmonisation of two middle voices, guided parallel in simple (soprano) and half speed (bass). At the end Bach adds the notes “b-a-c-h” as his musical signature.
Naturalness sound and contrapuntal mastery, combined with the forms of canon and chorale, creates this incomparable quality of Bachs impressive and magnificent organ work.