Due to the large amount of chormaticism embedded in Chopin's Mazurka in F minor, Op. 68, No. 4, it is difficult to apply harmonic analysis. The chromaticism can be seen straight away in measures 1- 8. The embellishments played here are B natural, D natural, A#, Fb, Gb, Cb, E natural, A natural, G #, and F#. It is definitely identifiable that the section is in F minor, but chord analysis is not really necessary. Beginning at measure 2, every two measures there is a sequence. The phrase desecends by a whole step at each new seqence. In addition, the last two measures of this entire phrase ends in a i chord at measure eight.
Measures 9 - 14 are similar to measures 1 - 8. The only difference is that it's set higher. But it has the sequence pattern. However, the cadence at the end of measure 14 is a half cadence in the key of A major. The modulation to the new key occurs by sequential chromaticism.
The section that consists of measures 15 - 23 begins in A major, but at measure 19 modulates back to F minor. This continues and there is a solid ending pac in F minor in measure 23.
At the beginning of the phrase in measures 24 - 32, the key is set in Ab major. Ab major is of coruse the relative major of F minor.
From measure 32 - 35 there is a desecending fifths sequence. Measures 32-40 is a very interesting phrase in general because some measures there will be two different chromatic notes with the same letter name. For example, in measure 36 there is an Eb and an E#, and in measure 38 there is a D natural and a Db. At measure 40 the performer returns to measure 2, but it's interesting because there is no official fine. The best place to end this piece would be at measure 23 because it holds a sold F minor chord, the key the piece originally begins with.