Chopin Polonaise in Aflat Cadence

[billybraga]

Hi, im very curious about certain patterns of some compositions, one of them is this strange cadence of Chopin's Heroic Polonaise that i want help to understand. What type of scale is this? He wrote an upward Ab major scale, but with the A natural. This A Isn't supose to be a half tone below? 

[pianowhisper]

The A is by all means supposed to be played natural!
The scale falls into an ascending B-flat melodic minor scale (it has all the notes of a B-flat major scale, except for its 3rd (D-flat) which obviously is minor). Notice how it ends on a B-flat and it has a certain feel of resolution. Of course, it doesn't really "sound" like a resolution since all the piece is being played in A-flat major.

[quantum]

Think of the scale as B-flat minor (melodic ascending), that starts on an A.  The chord that precedes the scale is B-flat minor and further enforces the harmony of B-flat minor, so we can think of the overall tonality of the measure as being in B-flat minor. 

Take the grouping of five bars, starting at the measure that precedes the scale, up till the arrival on the A-flat chord.

Bar 1: B-flat minor and E-flat minor chords
Bar 2: B-flat minor scale
Bar 3: E-flat major
Bar 4: embellishment
Bar 5: A-flat major

We can see in this way:

Bar 1: embellishment of B-flat minor, by alternating with it's iv, E-flat minor
Bar 2: embellishment of B-flat minor, by using the B-flat minor scale
Bar 3: arrival at E-flat major, and subsequent chordal embellishment
Bar 4: embellishment continues
Bar 5: arrival at A-flat major


These five bars represent an expansion of the ii, V, I progression in A-flat major.