: measures 19 to 34

The second section begins in bar 19 and is highly chromatic, contrasting with section A.

• In measure 19, Chopin switches to the key of A major.
• Measures 19 and 20 are then repeated in C# minor (measures 21 and 22) and E major (measures 23 and 24).

Several parallel dominant seventh chords descend chromatically in measure 24.:

How can we explain this passage?

The easiest way is to use the tritone substitution concept. In jazz theory, a dominant chord can be substituted for another dominant chord that shares the same tritone. All dominant chords have a tritone between their third and seventh notes. The two chords that share the tritone are a tritone apart.

The following image shows a cycle of fifths progression starting on E7 and ending on F7. The second system shows the same chords with tritone substitution applied to every other chord. Note that we arrive at the same chords as Chopin.

A more traditional explanation is also possible. The dominant seventh chord is enharmonically equivalent to the German augmented sixth chord. For example, E7 is equivalent to the augmented chord in the G# minor key. Each dominant chord can be used as an augmented sixth chord of the next chord in the sequence, descending chromatically as the augmented chord resolves:

Measures 27 to 34

Measures
27	E major key.
28 to 30	Chopin uses the IV chord in the key of E minor (modal interchange).
32 and 33	G-sharp minor (the third degree of E major) is transformed enharmonically into A-flat minor.
34	The Ab minor seventh chord leads to the Ab major chord in the next section.

© 2019 José Rodríguez Alvira. Published by teoria.com