In footnote 32 to my "Ascending Urlinie" article, I included the Haydn Piano Sonatas in Eb and Ab—the slow movement of the former (Hob. XVI/52, II), the menuet of the latter (Hob. XVI/43, II)—among pieces that use one of the variants of the rising line: the form ^5-^6-(reg.)^7-^8.Yesterday I wrote about the Ab menuet; today, the slow movement of the Eb sonata. And again I am making use of my holograph analytical sketch from 1982. See the entire sketch here: page 1 link; page 2 link. Score links: page 1; page 2.
The opening phrase is more easily read from ^3 than from ^5: the end of the initial tonic prolongation is at the 32nd note topped by G#5. I chose ^5 because of its longer-range implications, specifically in the internal reprise within the A section (more on that below). My sketch of the opening, then, consigns ^3 (as G#5) to a convoluted unfolding pair; I marked it "over" for "overlap" because that's the term that my mentor, Allen Forte, used (see his Schenker textbook co-written with Steven Gilbert).
In the elaborated restatement ending the A section, ^5 (B5 in the second measure) is more obviously a cover tone, but it is the sudden sweep up from it to E6 that is the major expressive event. This radical expansion of the upward leaps from the opening bars starts a chain of leaps: B5 to E6 in the fourth measure and G#5 to C#6 in the fifth measure. The line splits at the first of these (see the two ^5s marked in the score and the branching lines in the sketch), the lower one reaching G#5 and the upper one taking C#6 before both lines drop an octave over the dominant, G#5 to F#4 and C#6 to D#5.
