Trois Nouvelles Etudes- No.2 in AbM by Chopin: a look at Harmony/Tonality

I am currently studying this piece and think that it is wonderfully interesting in its use of harmony and tonality, because it seems to change its tonality (and at the very least, it's different harmonies) a lot. The piece was written in 1839, as part of a collection of pieces written as instruction for playing the piano.
The piece starts in AbM, but in bar 4 Gb's come in, and this lasts for 5 bars, putting it into DbM. It is immediately apparent that the piece has come into the subdominant key. Next however, the G's are again naturalised (middle of bar 8), so we go back to AbM. Then in bars 17 and 18, there are lots of accidentals which appear to change the key about- although many of the accidentals written are simply enharmonic equivalents of notes already in the key. Later, in bars 25-29, we get a passage where the key does change a lot, from Cm to C#m, to Dm, to D#m, and finally to Em. This chromatic section builds tension, up to the release when we arrive at Em- the dominant key. A bar later both the Db and the Ab are naturalised, putting us in BbM. A bar after that, the Eb is also naturalised, putting us in FM. Later we return to the A section of the piece (which starts in AbM and continues on to the aforementioned keys). For the end of the piece (bars 49-60), the piece returns to AbM, and apart from bars 51 and 52 where the Eb is naturalised, briefly giving a bit of interest but not altogether changing the key, we remain in AbM until the end.
As for the structure of the piece, the overall structure (macrostructure) is ABA (binary), and the microstructure is that both hands maintain their jobs throughout, with no overlap in what they do. The right hand has its chords played in a triplet rhythm from bar 1 to the end of the piece, whilst the left hand has quavers that directly go against the right hand rhythm, which have large intervals between each note, and more importantly, each pair of quavers.
There are very few dynamics written into my copy of the music (which is an Urtext edition), which indicates that Chopin did not include very many into the original. The only dynamics that there are are a  p at the very beginning of the piece, so that the beginning of the piece comes in very quietly, paving way for the rest of the piece's drama. The next, and final dynamic marking written in is a [f] in bar 29, this means that it is editorial, and Chopin probably didn't even want it written in. It comes directly after the massive chromatic build that we get in bars 25-28, thus emphasising that this part is the climax of the piece.


This is a performance of the piece by the amazing pianist Anthony Horowitz. (I love his use of voicing!)