I had a discussion with a few people on Chopin's Nocturne in B-flat minor. We couldn't reach an agreement and I'm curious how people would analyze it.
In the middle section of the piece (which is in Db major), there are occasionally some short phrases that are in D major. And the topic of the argument is whether those D sections are modulations to D. Let's call the first measure from top measure 1.
What we all agreed
- The second beat of m7 is the pivot of the "change". The Db at the bottom is spelled enharmonically as C# (the 3rd of V7 of D major). With the help of arpeggio and slower melodic notes, it lands naturally to the tonic on D major.
- There is one Dominant-Tonic progression from m8 to the first beat of m9. It's a I-IV46-I progression that can be considered a reinforcement of the key.
What we didn't agree is whether m8 and m9 is a modulation to D.
- The melodic material simply comes from m3 and m4.
- (What's after m9 is exactly the same as m2.) After m9, it simply comes back to Db major and to the exact same melody.
- The only reinforcement of the key D is the IV46-I progression which is a weak one. And there are no other reinforcement - no cadence at all.
So I would rather consider this a tonicization to D major, which is a non-diatonic chord on Db. That's what makes this part very interesting. I'd argue that Chopin simply wanted to play the same materials briefly in a foreign key (to bring some interesting colors) before it comes back again to the same materials - a satisfactory return like a tiny recap section in a sonata form. Since it's too short, and doesn't have brand new materials, I don't think this is a modulation.
Here's what they argued
- A single reinforcement like the one in m8-m9 is a clear sign of modulation.
- Tonicization doesn't come back via dominant-tonic progression like the one in m2.
- They further stated that this is analyzed as a modulation in a textbook written by Igor Vladimirovich Sposobin (I verified that it's true), as well as exams and textbooks used by conservatories in Poland and Germany (I couldn't verify this).
I just wondered, did I miss anything in my analysis? I know that there are different theories and definitions so it's very natural to have different understandings of modulation and tonicization. But if it is used in textbooks and exams in Chopin's homeland, it probably means no ambiguity here.
What I was taught in my university (not a conservatory obviously), is that as a traditional composer in common practice period, one would clearly establish the key. A lack of clear intention on modulation, is NOT a modulation but rather a tonicization or something else. But here for this example, it would probably be a creative use of tonicization since it tonicizes on a chord that's not in Db major.
Thank you for the patience if you reach here and I'm curious about what people might think on this.