Question: I wanted to highlight a particular chord of my [previous question](https://music.stackexchange.com/q/114106/77758) because it was bugging me a bit. What would you call a dominant triad over a subdominant bass, in pop/jazz roman numeral analysis? It could be seen as a `V7` in third inversion, but if you have a strong subdominant bass it doesn't really sound like it. But just calling it a `IV` seems... meh. Especially because we call the inverse, a subdominant triad over a dominant bass, a sus chord.

**Update**: Thanks all for your responses. As most of you have said, roman numeral analysis isn’t really suited for these kinds of chords. I might decide to just slash chords for bass and then come up with a different way to notate secondary chords and modulations in a functional manner. I don’t want to do this literally because that doesn’t make sense in a tonic-agnostic notation.

[![Sample](https://i.stack.imgur.com/MbtNF.png)](https://i.stack.imgur.com/MbtNF.png)

Answer: 
In your last question, you engaged with the common-tone diminished seventh chord (CT°7). But diminished sevenths aren't the only possible common-tone chords; another common possibility is the common-tone dominant seventh (CTV7), which I would argue is what we have here.

This is especially common with IV moving to V above a scale-degree 4 pedal, as it does here. And it's exactly the same as the opening of ["Part of Your World"](https://www.youtube.com/watch?v=SXKlJuO07eM) from *The Little Mermaid*: "Look at this stuff" is above a IV chord, and "isn't it neat?" is above a CTV7, that V42 where V is above a pedal of scale-degree 4. It resolves back to IV on "Wouldn't you think..."

I think this label is better than understanding that middle chord as a true V42, because in most cases that V42 is going to resolve to tonic (and typically in first inversion, but that changes based on style and genre). Here it's clearly prolonging IV, and since common-tone chords are inherently prolongational, I think the CTV7 is the best interpretation.
I agree that these are modal 'color' chords over a pedal point. The V chord is not functioning as a dominant at all; rather, it brings out the Lydian nature of the IV chord. The Lydian mode gives that faraway, otherworldly sound, and is especially exploited in cinematic music.

You might have better luck with pop/jazz music notation, even though you lose the tonic-agnostic benefit of roman numerals. Check out this excerpt from a jazz lead sheet:

[![Jazz lead sheet excerpt](https://i.stack.imgur.com/V2ZI9.png)](https://i.stack.imgur.com/V2ZI9.png)

Here we see chords progressing over pedal tones. The emphasis is on readability. Functional analysis is left open to debate - this kind of music can have multiple, overlapping harmonic interpretations.