Prelude No. 12 in G# Minor by Frédéric Chopin

Measures
29	The G major chord in the previous phrase leads to C major, which is the sixth degree of the E minor scale.
36 to 39	The E minor dominant chord is used as the augmented sixth chord of D# minor.
40	The D# minor chord transforms into a G# minor dominant chord, which brings us back to the main key and prepares the recapitulation.