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 any of our known functions, so you needed to examine the context of this example.
The chord following the G minor triad is a clear V</sup>4/2</sup>/ii which then resolves to a ii chord. If you look at your leadsheet, you can clearly 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 iv/ii – V</sup>4/2</sup>/ii – ii. Without a firm cadence, we have not changed keys here, 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, the A minor triad, is clearly a vi chord in the key of C major. It is worth noting however, that because this chord is followed by a secondary dominant, this chord also functions perfectly in the secondary key as a non-dominant secondary function. The third chord is a V</sup>7</sup>/V which tonicizes the key of G major. If you extend this key backwards, the A minor chord functions as a ii/V chord.
I would never label this as anything other than a vi chord in C major, because it is fulfilling its standard diatonic function in every way. However, this should further illustrate how fluid harmony can become when thinking of the relationships between keys and voice-leading.