How could these chords in Debussy's "Reverie" be analyzed?

Question

I am working on a harmonic analysis of "Reverie" by Debussy, and I am trying to find ways to analyze two things.

1. In the first image (mm. 24–35), the first few measures are in the key of B-flat Major, and it is a Imaj7 chord. Then there is a transition that leads to the key of C-Major. How would you analyze these chords with the C-sharps? Would you call it F+/G? And would you say that it is followed by G7sus2? Is there a good way of explaining the function of the augmented chord?

2. In the second image (mm. 48–58), the first three measures are in the key of F-Major. This then moves to the next section of the piece, which starts with the Dm and E chords. Would it be best to analyze the start of this section as the key of A harmonic minor? The first cadence here is a PAC in F-Major, and the second one is a PAC in E-Major. I don't know if there is a good way to analyze the function of these Dm and E chords.

If anyone has thoughts on ways to analyze these different chords, I'd love to hear them! Thanks in advance!

Question #1

Question #2

Answer 1

The augmented chords

The overall harmonic progression in mm. 24–32 is:

mm. 24–26    27    28    29    30–32    32(beats 3–4) 
    Bb       F+/G  Dm/G  F+/G  Dm/G     G

The Gs that appear in bars 27–32(beats 1–2) serve the function of a pedal tone. This can be tested by playing the passage without them — just replace them with F+ or Dm chord tones: the overall harmonic sense is maintained.

The chords themselves are understood in terms of the voice leading:

Bb  F+  Dm
--  --  --
F   F   F
D   C#  D
Bb  A   A

The Dm/E chords

These are set up by mm. 35–36 and mm. 37–38, shown below, which move from Cm to D, respectively — the same relationship as Dm to E. Mm. 41–42 introduce the pitch G# into the piece, which also helps prepare the ear.

The Dm is initially the relative minor of F, where we just cadenced, so the ear accepts it easily. And the transition to E has been prepared as described above.

A key detail in the oscillation between Dm and E is the "alto voice", which has moves between the pitches D and B. This happens several times over the course of the next few measures, and the intervallic relationship sets one up to hear the "soprano voice" at the end of the section, which moves between E and C#.

Reverie mm. 36–39

(Image source: IMSLP)