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. Chopin's Nocturne in B-flat minor

What we all agreed

  1. 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.
  2. 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.

My arguments

  1. The melodic material simply comes from m3 and m4.
  2. (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.
  3. 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

  1. A single reinforcement like the one in m8-m9 is a clear sign of modulation.
  2. Tonicization doesn't come back via dominant-tonic progression like the one in m2.
  3. 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.

  • 2
    It would be worth clarifying whether any of the books referenced by your friends made any distinction between modulation and tonicization. That is, do the books contain separate vocabulary for each concept, and do they contain differentiated examples of each? Should we allow for the possibility that those books only use one term – modulation – for any modulation-like occurrence?
    – Aaron
    Oct 5, 2021 at 6:31
  • @Aaron. I finally figured out how to register my unregistered account and can comment now! They only ever mentioned 1 textbook which is a widely-used textbook in their conservatories. I just read the chapters and there are dedicated ones for modulation and tonicization. It also mentions that "The main characteristic of tonicization is the lack of reinforcing cadences". Based on this definition, this section is clearly a tonicization.
    – lbbl59
    Oct 9, 2021 at 22:08

3 Answers 3


Can you tonicize to a chord that's not on the original key?


This is not only "allowed", but commonplace, especially by the time Chopin was composing. One of the compositional goals of Chopin and his contemporaries was to explore chromaticism, even to the point of hiding the actual key of the piece.

Is this a tonicization or a modulation?


I would call it a tonicization because of its brief duration and because there is not a complete phrase in the new key.

Is this specific "tonici-modulation" in the original key?

No ... or perhaps yes.

This, too, is a matter of interpretation. Consider that the apparent A7 chord is enharmonically equivalent to Bbb7, which is bVI in Db major through modal mixture from Db minor. And the D7 chord is enharmonically equivalent to Ebb7, which is bII in Db major. So we have (bVI = V/bII) -> bII.

bII is a common enough occurrence to warrant its own Roman numeral designation. So is it "part of" the original key, or is it a foreign key? Either answer is acceptable, but I would suggest the presence of G major (or, Abb major) is a step too far to consider the music still to be in Db major, as it is "genuinely foreign" to that key — neither native to Db major nor available through modal mixture.

  • It's also worth noting that this "VI7" is really an enharmonically spelled German augmented-sixth chord in the original D-flat.
    – Richard
    Oct 5, 2021 at 11:43
  • @Aaron , thanks for the detailed discussion! I'd agree 100% that this section is too brief to be a modulation. "Consider that the apparent A7 chord is enharmonically equivalent to Bbb7, which is bVI in Db major". Good callout! I didn't think of that! However, if this was Chopin's intention, he would have spelled it this way. But yes! This is true in its sound.
    – lbbl59
    Oct 9, 2021 at 22:09

A secondary dominant creates a brief ’tonicization’. A more extended visit to a different tonality is labelled a ‘modulation’. There is a middle ground, in which we can argue between the two terms.

And does it really matter that much where we stop saying ‘V7 of IV’ and admit that there’s a new I? With the exception of a ‘Truck driver’ modulation - shifting up a key with no intention of returning - a change of tonic always relates to the original key. We’ve taken a journey, but home is still home. Maybe the journey leads somewhere we like well enough to build a house and linger for a while, maybe it’s just a hamlet we speed through without stopping. A matter of degree, not a fundamental difference.

And yes, a tonicization, a modulation, and anything between can be to any key, not just a diatonic one.

  • Would it be fair to say a secondary dominant that actually went to that 'new' tonic chord/harmony? Not all sec. doms actually do so.
    – Tim
    Oct 5, 2021 at 11:02
  • A dominant tends to a tonic. That's the basis of Common Practice harmony. Sometimes the tonic is achieved, sometimes it isn't. Sometimes it's reached and established as a new key centre, sometimes it isn't. What matters is that we recognise the effect of functional progressions and the effect of contrasting keys, not whether we label borderline instances as temporary or established.
    – Laurence
    Oct 5, 2021 at 12:10
  • @LaurencePayne, "What matters is that we recognize the effect of functional progressions and the effect of contrasting keys, not whether we label borderline instances as temporary or established." This is a great way to put it. I think this is definitely the ultimate goal of listening and composing. Yet, if we do have evidence to support a particular direction on the spectrum, we should make the distinction. Otherwise we may miss the interesting parts :)
    – lbbl59
    Oct 9, 2021 at 22:15

In romantic pieces, wherever you see diminished chords, you can expect to arrive at a new key-- possibly a tritone away.

So I'd expect D♭-G, rather than D♭-D. You might also reasonably expect to see a modulation to E or to B♭, as those are the other keys outlined by the same o7 chord.

In bar 1, the o7 is G-B♭-C#-E, leading to A♭, the V of D♭.

In bar 7, Chopin uses an A7 chord instead of C#-E-G-B♭, and the doubled C# really pushes up toward that D. But to me, bar 8 is a mini-pedal over D (i.e. in G major), rather than a cadence IN the key of D.

  • I think there's even less clue in the section that indicates a G major. " rather than a cadence IN the key of D.". Yes, it's not a cadence, but it is part of a I-IV46-I progress that makes more sense in D than a V-I46-V progression in G. Considering the melodic material, the melodic material starts on I and it's also on the strong beat.
    – lbbl59
    Oct 9, 2021 at 22:42
  • @lbbl59 If you isolate bars 7-9, that's a sensible view. In analysis of the whole, we need to look for similarities and differences. My analysis is this: the Go7 chord in bar 1 prepares for A♭7, the V of D♭. In bar 7, the A7 chord (which is essentially the same as Go7) prepares for D, the V of G. The question is whether that similarity between Go7 and A7 justifies calling a section with no G in the bass "in the key of G." For me, yes. For you, no. That's how it goes with ambiguous or complex passages. Oct 9, 2021 at 23:14
  • "look for similarities and differences". True, but I'm afraid you were comparing unrelated measures. m.9 is what is the same as m.1. There's a measure before m.1 that is the same as m.8. I was taught we should look for direct answers and not overthink. Here they don't establish a pattern so the direct answer is D (plus the evidence I mentioned earlier). But if you HEAR it that way, cool :)
    – lbbl59
    Oct 10, 2021 at 6:45
  • I have trouble understanding that °7 chord. It's vii°43 in D which makes less sense in G (#iv°43?). Skipping the V, it can be heard as CT° but spelled wrong and is too far from the resolution. With the V, it's a dominant of dominant but also spelled wrong...But if I must make a choice here, I'd treat it as a V of V here (it's also how I hear it).
    – lbbl59
    Oct 10, 2021 at 6:49

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