F. Chopin: Waltz in C# min Op. 64, No. 2
Diatonic Analysis

Other sources about this piece are located here.

The structure of the piece is quite simple. It has three main parts. Each part has two halves that are similar.
There is another interesting characteristics. We can see that the first two parts are in E major scale, the third one is in Db major. When we look at the two first parts more closely, we see that they are not in major mode, but in minor (6 - aeolian) mode. It is C# minor (as stated in the title of the piece :)). And C# equals to Db. The conclusion is simple. The whole song root is C#. First two parts are minor (aeolian mode), the third one is major (ionian mode).

Let's look at the diatonic chart - Part 1:

We can detect usual bass line 1 4 (->tritone)7 3 6 2 5 1 TT 7 3 6 starting at bar 8 (more about important interval - P4up maybe later in general mathematical view at music). But there are more instances of it.

Part 2:

Part 3:

Everything just usual and expectable structures. Just to take, realize and apply.
In bar 72 we can see chord 7, although we marked it as diatonic non-standard chord. It can happen that this chord appears and we can't label it as a form of 5 or 2 chord. We can consider this an exception to the rule.

Chords: