I've been told that you have to analyze progressions according to the key at the end, despite how many keys/tonality that precede it. Is this true?

If a composition contains one key in long duration, but end up in another key with just a slight cadence at the last measure should it be also analyzed by its last key or should we assign The Roman Numerals according to what key it's in at the moment?

3 Answers 3


I agree with Alexander, and I think it also depends on how long you're in a different key. Full phrases and sections should likely be analyzed in their new key, but one or two borrowed chords can remain the the original key. To use Alexander's example, the C7 chord could be labeled as V7 of V (V7/V). I'm also assuming you're speaking of classical music. Jazz-wise, especially Bebop, songs tend to change keys very frequently.

  • 2
    Aye, there's also the point of if you're in a transitive(temporary) or full modulation, because if it's only for 8 bars you could argue both ways! Apr 20, 2014 at 8:09
  • Just to clarify for others: transitive / temporary modulation also means tonicization. Apr 20, 2014 at 15:15
  • Assuming the harmonic model is I IV V I with a large tonicization on IV. Region IV would sound like the main key. The distinction between tonicization and modulation is rather umbiguous.
    – Green
    Apr 21, 2014 at 10:23

Generally, you analyse music based on the key it is currently in, however there are cases where you can analyse in 2 keys at once(Specifically when modulating).

Say for Example you were in the key of C and modulated to G like so the chords could become something like:

    C e am C | G e am C7 |G(now in the key of G)

In the 1st bar, you're clearly in C, but for the second you can either analyse in the key of C OR the key you are going to. Let's do that now

In C

G e am C7 
V iii vi I7(note that in C, the lasy Chord should be CM7 instead)

In G

G e am C7
I iv ii V7

notice that the shared chords between C and G make this progression not only fit with G major, but actually fit better than with c major!

in notation from what I know the whole thing would likely be notated like so

     C e   am C| G e   am C7|G
     I iii vi I| V iii vi I7|I
                 I iv  ii V

and in that case as you can see, there are 2 keys being analysed at the same time. Hope that helps :)

  • you're right, the analysis will work well as the chords are shared C being very closely related to G. I'm intrigued as to why one would use C7, or Cmaj7 to get to G. In fact, in the example, it could be argued that no modulation has occurred. After all, the 2nd bar started with G, but was there vmodulation there? Often, to modulate, the V of the 'new key' precedes it, as in D or D7/D9, using slightly different notes from the original key. That's how we know it's modulated, surely.
    – Tim
    Apr 20, 2014 at 9:21
  • oh bugger, I've gone the wrong way! rewrite time! Apr 20, 2014 at 9:43
  • Only trying to help !!
    – Tim
    Apr 20, 2014 at 10:46
  • The IV of G is "C", not e minor. The V of G is "D". Also, the dominant of the new key is typically predominated by a pivot chord. The suggestion of key-based analysis is only one type of analysis - specifically vertical analysis. If you analyzed the piece linearly through counterpoint, the harmonic landscape would change. Further, if you used Schenkerian analysis, the harmonic landscape would again change even more so. Incidentally, C-em-am is an incredibly weak chord progression. Apr 20, 2014 at 15:14

Assuming the piece ends in the written key, it makes sense to analyse it from that standpoint. However, if it has modulated, it makes little sense. The original key signature has to be the giveaway - that's surely the key/starting point that the composer wanted, so it's the datum point.It's rather like a journey - you need to know where you are at the beginning, in order to find a route to your destination. You wouldn't find your way otherwise.

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