I said the movements were based on dances, but modified considerably. The first one uses the mazurka rhythm, but the second, based on the Ländler, a folk dance in 3/4, has a melody that suggests duple time. The third movement is a waltz, but the two hands move out of phase with the left hand coming ahead of the right. In the fourth piece, the hands are a half beat apart. The sixth piece is recognizable as a tarantella, a high-velocity dance from Italy usually in 6/8. Schumann outdoes himself with this one by displacing the accents, usually on 1 and 4 (123 456) to 3 and 6 in the right hand simultaneously with 2 and 5 in the left hand!
But it is the harmony that is even more striking. Instead of introducing the tonic key, he slowly reveals it. The basic tonality is B minor, but the first dance is in G major. The work as a whole is divided into two books of nine pieces each. Both books end in C major! So why do I say that B minor is the basic tonality? Schumann is working with ambiguity here; distance and instability are both important devices in his harmonic conception. The note B is often used as an important pivot, such as between the first and second pieces. More significant is the return of the second piece, in B minor, nearly a half hour later--the only music to be reprised. The fourth piece is very solidly in B minor as well. In the second book, the second and fourth pieces are also in B minor. The seventeenth piece is like a distant echo of the slow ländler of the second piece. It all could end here, unless you are Robert Schumann. Instead, written over the score to the eighteenth and last piece is this:
"Superfluously, Eusebius added the following, and his eyes filled with tears of happiness."I have talked before in various places about how two important harmonies were a constant resource in the early 19th century--they were a Romantic staple. These two harmonies are the flat submediant (A flat in C major), much used by Schubert, and the Neapolitan, the major chord built on the flat supertonic (D flat in C major). But this is the first piece I know of to end on the Neapolitan! C major is the Neapolitan of B minor. Here is Charles Rosen, who is also a wonderful pianist, playing the last three movements, XVI to XVIII:
You can find the complete score here and Rosen has a detailed discussion of the piece in his The Romantic Generation on pp. 223 to 236.