A simple diatonic mediant move (effecting the transformation R twice) is aligned with formal design in an early ternary waltz that also happens to contrast Ländler and deutscher traits (the former in the main theme, the latter in the contrasting middle) using sharp dynamic contrast to make the point unmistakably.
"Deutscher" here was a bit too confident -- I was relying on expressive and functional distinctions that often appear in and between Schubert's dances. First, recall that "deutscher" was a relatively broad category referring -- especially very early in the nineteenth century -- to all the waltzing dances. It was, in effect, the German "back-translation" of the French appellation from the 1760s, allemande (in contredanse allemande).
Second, "deutscher" was used more narrowly for music that had the processional (that is, somewhat formal) character of the menuet; by 1810, it was often impossible to tell the two apart -- to a composer, the deutscher was often just a menuet with few of that genre's long-since-clichéd gestures. It was the contrast between the processional "waltz" (deutscher) and the romantic couple dance of the Ländler that was clearly meaningful to Schubert and that I was relying on.
But, third, the foot-stamping segments of a folk dance could also be represented along with the drone instrument (bagpipe, Dudelsack, etc.) that accompanied folk (rural) dancing well into the nineteenth century (Petermayr, 83-84).
In other words, here Schubert is offering us two very different sides of his tune: as sweet Ländler in the first strain, but probably as accompaniment to rural stampfen thereafter, not to a more refined urban processional dance.
In the course of this, he might even have been duplicating the contrasting segments of rural or lower-class group dancing. Petermayr quotes a description of such dancing from later in the century (NB: the segments are marked by numbers in square brackets):
The string players have tuned their instruments and begun to play dance music in three-quarter time with their characteristically piercing tones, while they stamp their feet in duple time. [1] The dancers don't hold back: pair on pair they step into the line of dance and go some steps forward, following the beat, man and woman side by side (specifically, with the woman on the outside). [2] Then they grasp hands and make several turns [or figures [the word is Schwenkungen]], so that the woman appears briefly on the inside then again on the outside of the line. Then both raise their arms high above their heads and the woman turns herself once under the man's arm. [3] Then both settle back [to side-by-side position] and execute several figures, as before. [4] Again the arms go up and the woman turns quickly twice, so that her skirts swirl upward and out. [5] Each couple then embraces [that is, takes a clasping hold] and turns waltzing in a circle. [6] Again the couples settle back, but now the dancers move forward stomping on the floor so vigorously that the windows shake and the dust rises. While doing this they clap hands in time, call out, and sing in chorus the powerful, not easily forgotten "Schnadahüpfl" [also known as "Vierzeiler" -- commonly known bits of verse, sometimes nonsense]. [When all this is done,] the couples change, as each woman moves forward up the line to the next man, and the whole sequence begins again. This is repeated as often as there are dancing couples, so that at the end each man has his original partner. (94-95; trans.)
Reference.
Petermayr, Claus. "Nieder- und oberösterreiche Quellen zum Volkstanz im Biedermeier." In Harrandt, Andrea, and Erich Wolfgang Partsch. Tanzkultur im Biedermeier: wissenschaftliche Tagung 1. bis 2. Oktober 2004, Ruprechtshofen, N. Ö, 75-96. Series: Publikationen des Instituts für Österreichische Musikdokumentation, vol. 31. Tutzing: Hans Schneider, 2006.
