Final Measures

Measures 19 and 20 are exactly the same as measures 5 - 6. They are a recapitulation before a coda to end the prelude.

In measure 21, Chopin starts an ascending progression that goes to B minor, C# minor and finally G minor. In measure 22, the V7 of G minor is used as a German augmented sixth chord of F# minor to prepare a coda in this key:

Recording courtesy of Robert Ståhlbrand and Piano Society

Notice the Neapolitan sixth chords used in bar 24:

Recording courtesy of Robert Ståhlbrand and Piano Society

Measures 27 and 28 are repeated in F-sharp major, followed by a final cadence that also uses a Neapolitan sixth chord:

Recording courtesy of Robert Ståhlbrand and Piano Society