William Rothstein, Like Falling off a Log: Rubato in Chopin's Prelude in A-flat Major

Example 1. Chopin, Prelude No. 17: outline of the form
 

measures 1-2 3-18 19-27 27-34 35-42 43-57 57-64 65-84 84-90
# of mm.* 2 16 9 8 8 15 8 20 7
key Ab Ab A(?)E Edim. 7 Ab EEb Eb Ab Ab
cadence(s)   HC, PAC PAC   HC PAC   tonic pedal tonic pedal
formal part intro. A1 B codettaretrans. A2 C codetta A3 coda

* Measures 27, 57, and 84 are counted twice