Chromaticism
A student asked me for an example of a V/V chord used within the context of a song. The image below links to a brief video describing how I used V/V in the relative harmonic minor of Gb Major (Eb minor) to shape emotional pull in the harmony. In the key of Gb major, iii is a naturally occurring minor chord. Raising Db to D natural, to make a major III is what makes all the difference!
Another way to analyze this chord is to think of it as flat (b) II, or a Neapolitan Chord (N) in the Relative Major of Gb/F# minor (the Parallel Minor of my key). The reason for this is the way that I chose to resolve the chord. The Neapolitan chord traditionally resolves to the dominant (V) of the key in which it appears. The half step motion of the root of the Neapolitan chord resolving up to the fifth of the dominant, as well as the falling half step motion of the fifth of the Neapolitan resolving down to the root of the dominant creates a strong chromatic pull. For these reasons the Neapolitan chord traditionally serves a chromatic function within a progression. In the case of A major (the relative major of our parallel minor key, Gb/F# minor), this would be B flat resolving up to B natural and F natural resolving down to E natural.
Since I am not in A major, my next chord is not E major (as it should be if I am resolving a Neapolitan to the dominant (E major) of my key, A major). I do however resolve to another borrowed chord that plays a crucial role in my chromatic movement back to the tonic, Gb major; the minor iv, a borrowed chord from Gb minor. The only difference between the half step motion in this resolution and the one I just described, is that instead of F natural resolving one half step down to E natural, it resolves one half step up to Gb/F#. I then make another small chromatic shift to the traditionally occurring major IV chord in the key of Gb major before resolving back to the tonic (Gb major).
It is because of my chromatic motion to minor iv that I find this second analysis to be a more comprehensive way of describing the function of each chord within my progression; particularly because I am playing open fifths throughout — only hinting at major/minor sonority with clever chordal interplay, therefore placing greater emphasis on the chromatic motion of the progression. This analysis is however much more advanced and requires a deeper understanding of music theory to fully appreciate. You could also simply call it flat IV, though I never actually play Bb and D natural at exactly the same time while free of other sonority-altering notes, thus eluding this obvious harmony.