Only after nine additional measures does the figure assume its final form, as a compact, shapely motive pure and simple

from which Bach constructs what might be called (to risk a contradiction in terms) a rising cascade:

The mounting glory of these measures is enhanced by their being cast, as none of the Kyrie has been until now, in a major key, or rather in a “chain” of major keys, each serving as the dominant of the next:

This passage leads, by way of contrast, into the piece’s most pensive stretch, a duet between alto and tenor that presents the subject in an uncommonly beautiful stretto (an overlapping of statements):