TONICIZATIONS
A tonicization is a temporary usage of the diatonic tones from a tonality other than the current one i.e. a temporary shift in the tonality. Since its character is temporary, it is not considered as a change of the tonality. Thus, the tonality remains the same during and after a tonicization and a new key is not annotated. The diatonic and altered tones were explained in chapter Diatonic and altered tones.
We already saw examples of tonicizations: secondary chords and tonicizations of the Neapolitan chord. In chapters Secondary chords and Tonicization of Neapolitan chord we did not annotate any new key during the harmony analysis.
Both modulations and tonicizations happen most often between closely related keys i.e. keys that are adjacent in the circle of fifths. Such modulations and tonicizations can be realized by changing only one note name and thus they tend to sound natural and not abrupt. The circle of fifths and closely related keys were explained in chapter Circle of fifths.
Modulation compared to tonicization
We must notice that both a tonicization and modulation are recognized in the same way, as the usage of diatonic tones from a tonality other than the current one. Therefore, to find a tonicization or modulation, we use the same procedure that was explained in chapter Key of passage, to find passages that have the persistent usage of diatonic tones from a tonality other than the current one. When we find such a passage, the question which arises is: did we find a tonicization or modulation? This decision can be subjective, but we can say that a modulation is found if the passage contains a non-trivial thought and at least one significant chord progression.
In chapter Chopin’s Prelude No. 3 in G major we used our best knowledge at the moment to try to determine keys that are used in this composition. However, we postponed finishing this task until we shall know how to analyze harmony. Now when we know about secondary chords, we are ready to finish this task. The next figure shows the harmony analysis of Chopin’s prelude No. 3 in G major. We see two typical usages of the secondary chords: the secondary dominant chord of V which resolves to the diatonic chord on V and similarly the secondary dominant chord of IV which resolves to the diatonic chord on IV. Thus, there are no modulations in this composition, only two tonicizations. That is, the prelude is entirely written in the G major key. Although in chapter Chopin’s Prelude No. 3 in G major we considered the possibility that the prelude visits the D major key and the C major key, we give up on this thought. Why? The reason is that there are no significant chord progressions that establish new keys. A single V I chord progression is not significant enough to establish a new key.
The next figure shows the beginning of Bach’s Prelude No. 9 in E major from Well-Tempered Clavier, book I. From the second half of measure 3, we can see the usage of the note name A# instead of A. This might indicate a modulation from the E major key to the B major key. Why? If we compare the diatonic tones of the E major key and the B major key, we see that they differ precisely in the note names A and A#. This is shown in the same figure. The same thing can be seen immediately by comparing only the key signatures.
We see that the mentioned usage of the note name A# instead of A, happens persistently in the following five measures. Also, in these five measures, we see chord progressions that establish the B major key. First, there is a chord progression P > D > T in the B major key, at the location of modulation. Then, there is a chain of idealized chord progressions T > P > D > T in the B major key. All this strongly suggests modulation to the B major key. In the figure, harmonic functions are also annotated. Harmonic functions were explained in chapter Harmonic functions. The reason why the E major triad chord is annotated in both keys (E: I and B: IV) will be explained later.
