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