I have a general question that the community seems to be at odds with concerning applied chords.
The point and emphasis of applied chords intend that they lead to another chord. The most common example I see is a V/i subjective context, usually in a minor mode, where a chord from the parallel major chord is inserted to lead back into the original i context.
What I don’t quite understand, is can this context switch be used instead of for parallel mode emphasis, but to emphasize leading into a relative chord use?
Notice how the tab is in fminor, yet employs a V/iv fmajor applied chord. If applied chords only worked for leading into parallel chords, then one would assume the second chord should be a Bflatmajor (from the parallel mode Fmajor). It is not. It is Dflat major. Why? Because the V/iv is not leading to the parallel modes (fmajor) scale. It is leading to the relative modes (Aflat major) iv chord, which happens to be, Dflatmajor.
This song never implies a major third above F. From what I can hear the chord progression can be more succinctly represented as isus4 - VI6/9 - iv without loss of information. There is no leading action in any part of the progression either; the tonic chord does not lead into the submediant, and certainly not into the iv after that, especially since this tonic chord is on a strong measure.
Again, the C♯ chord does not lead into the F♯m chord after that, since that chord is only a passing chord between E(add9) and G♯7. The tonic chord can readily borrow from the parallel major key without itself having to lead into any other chord, since applied chords imply resolution, thus the key is C♯ Minor and the chorus analysis is correct.
I - ♭III - ♭VI - V - ♭III - ♭VI, extensions omitted. This is a typical major/minor mixture; whether analyses should use the major or minor key depends heavily on which particular modes the melody supports, but when there is no melody at all, the major key should be chosen for generality. Applied chords on harmonically strong positions are rarely needed, except when they do initialize a tonicization or modulation or, in the context of classical music, sequence. (The ♭III should not be interpreted as V/♭VI, but this is possible if the chord contains a minor seventh instead of a major seventh, so that it can resolve into ♭VI according to this chromatic voice leading.)
Also major/minor mixture. Minor key is suggested since the measures containing the F chords also have the A♭ note somewhere in the melody and the accompaniment. (It is certainly not a 7♯9 chord.)
Applied chords work in relation to the destination chord. An applied chord must imply a resolution into the destination chord as it is written, except when the target chord’s major/minor quality differs and Hookpad cannot notate it.
if this is the case (and this happens a lot in music), why would the hooktheory difficulty api not support a tablature of this nature? should this be a feature request that borrowing a major I should not affect tab difficulty?
Chords supermodal in the relative major remove the complexity tag. Nobody knows why the developers measure chord difficulty in the relative major, though if the major V in minor (notV/i; the major V can replace V/i in a minor key, regardless of whether the chord has dominant function, due to historical treatment of the minor key) is made as an exception, then surely the major I in minor can be made as such too.
I assume the idea was to evaluate minor progressions in the relative major, because plenty of people think of i - VI - III - VII, for example, as vi - IV - I - V, but the idea completely breaks down with any other mode, especially in the search by chords feature. If someone wants to find, say, I - IV - vi, no Mixolydian tabs are going to show up, and nobody will think to search for V - I - iii to find those. Plus that would also return all the major tabs with that progression anyway. And the minor ones with VII - III - v, and the Dorian ones with IV - VII - ii, etc.