Secondary chords can be extended beyond the dominant function, creating further tonicization of a chosen chord.
For the following chorale, provide leadsheet symbols and a Roman numeral analysis. There are multiple chromatically-altered chords, some of which cannot be explained as secondary dominant or secondary leading-tone chords. And while it might be tempting to label a minor v chord in your analysis, that doesn’t explain what the listener is hearing. Instead focus on looking for “pockets” of tonality, in which you might be able to explain a progression easier through the lens of another key.
As with all analysis, you should never dwell too much on an individual chord in your first attempt. If you get stuck, just move to the next chord. It is helpful to start with leadsheet symbols when working with chromatic harmony, because it allows you to label chords by their construction before worrying about each chord’s function and relationships.
At first glance (and hearing), the G minor triad seems starkly out of place. We have seen minor v chords in previous examples, but in each case, they followed the defined conventions of one of our alternate functions such as a passing or pedal functions. Here, the minor v chord does not fit the typical voice-leading of tertiary functions–it does not create the passing bass line typical of passing chords, nor does it have an obvious pedal voice–so we need to examine the context of this example.
The chord following the G minor triad is a clear V6/5/ii which then resolves to a ii chord. If you look through your leadsheet symbols, you can see a pattern that extends backwards if you continue thinking in the key of ii (D minor). In the key of ii, a G minor chord is a diatonic iv chord, which would make this a iv-V-i progression in that key. Therefore, the correct labeling of this example is iv6/4/ii – V6/5/ii – ii. Without a stable cadence, we have not changed keys, but this progression clearly emphasizes and extends our pre-dominant harmony.
Because of the nature of diatonic progressions, there is a great deal of crossover between non-dominant secondary functions and the actual diatonic chords of a key. Provide a Roman numeral analysis of the following chorale, paying particular attention to the second chord. Is it diatonic or a secondary function?
The second chord, an A minor triad, is clearly a vi chord in the key of C major, and it should be labeled as such. It is worth noting, however, that because this chord is followed by secondary dominant chord of V7/V (the D major triad), the A minor chord also could be labeled in the secondary key as a non-dominant secondary function. The D major chord can only be a V7/V, but if you extend this toniciazation for another chord, the A minor chord could be labeled as a ii/V chord.
That being said, just because you can label something in a complex way does not mean that this is helpful in your analysis. Generally speaking, the simplest solution is the best, and in this example, I highly recommend that you label this as a vi chord in C major–exactly as you would have before you learned of tonicization. I find that exploring secondary funtion is an excellent way to illustrate the voice-leading foundations that drive harmonic progression, but complexity for complexity’s sake does not help explain how an average listener hears music, which should always be your goal when analyzing a piece.