from/to an inner voice, Untergreifen. This describes
a linear progression at a higher
level that connects a note of the Urlinie
with a note of an inner voice at a deeper level. An initial
ascent is an example of motion from an inner voice at a deep
level. In mm. 1-4 of the aria, the ascending fifth B$-F
is a motion from the inner voice (B$)
to the Kopfton of the Urlinie.
Mm. 5-6 exhibit another motion from the inner voice, from C to E$,
of the Urlinie. Such motions serve to prolong
the deeper levels.
The example below illustrates both types of motion as they serve
to prolong the 4
of the upper voice in Variation 16. Motion to an inner voice occurs
in mm. 14-19 of the fugue, where a third
prolongs the underlying harmony, I,
by moving from the upper voice, F, to the inner voice, D.