"Arabella," in Ab major, is a nocturne in the familiar Field/Chopin manner. The design fits the genre also: ternary where A is a 16-bar period with a sentence as the antecedent phase and with an embellished consequent, B is a 16-bar sentence, and the reprise of A is complete, but varied. A five-bar coda ends.
The structural cadence, ending the reprise, complicates the voice-leading in the right hand, but the motions are clear enough as outlined below. From IV6, an augmented sixth resolves outward to the octave—with Eb4 at the top—and then the parallel sixths that carry Eb4 up to G4 through the chromatic F#4 (which "might have been" ^6 otherwise), the octave doubling of C & Db (circled notes), and the traditional 6-8 close—the cantus-tenor formula—that amplifies ^7-^8 (as G4-Ab4).
Here is a slightly simplified version of the right hand tracing structural soprano and alto:
Here is the passage, simplified a bit more, with scale degrees for a primitive ascending Urlinie and structural soprano and alto.
And here is a final simplification, to remove the register changes in the alto voice and also the chromatic note, suggesting that a simple rising line abstractly underlies the passage.
