Prelude V ... Les collines d'Anacapri, Claude Debussy

Introduction and section A.

We will begin by discussing the rhythmic aspects of the Prelude. Debussy specifies a time signature of 12/16 and 2/4. The following image clarifies the relationship between these metrics and the rhythmic motifs that we will find in the Prelude.

The piece begins with the 12/16 used like a 6/8 (bar 1, rhythmic pattern A).
At bar 3 (rhythmic pattern B), we see the 12/16 bar. Note that Debussy does not add a dot to the last eighth note. We will have to analyze the context to know if the figures use binary or ternary subdivision through the Prelude. In this case, the last eighth note equals three sixteenth notes despite not having a dot.
At bar 9 (rhythmic pattern C), each quarter note subdivides into three 12/16 eighth notes and each eighth note into three 12/16 sixteenth notes.
At bar 10, we see pattern B in the upper voice and C in the other voices.

Introduction

The Prelude begins with an 11-measure introduction. The entire Prelude maintains the key signature of B major.

In the first two measures, five notes of the B major scale form a motif that we will call the pentatonic motif because of its pentatonic character:

At measure 3, a melodic pattern using a 12/16 metric appears, suggesting the G-sharp minor scale, which will develop as the main theme. The last eighth note should have a dot that Debussy doesn't write. We'll call this motif the 12/16 motif:

We repeat the first measure's pentatonic motif followed by a chord (a) made up of all the B major scale notes except D and F. The chord of the following measure (b) based on the pentatonic motif adds the F#:

The notes C and E are chromatically altered in measure 9. They resolve to the third and fifth of the B major chord in measure 10. The 12/16 motif is repeated a fifth higher on this B major chord to conclude the introduction. Notice the use of the ninth (C#) and thirteenth (G#) extensions:

The main theme (we will call it theme A), develops over an ostinato with the notes D# - F# based on motif 12/16.

The melody seems to rest on the G#.
Only notes of the pentatonic scale are used from bar 16 onwards.
We have added dots and some implicit sixteenth note duplets (indicated in blue).

Four measures over a dominant pedal, prepare a variation of the main theme. The left-hand plays the 12/16 motif and reaffirms the dominant harmony:

A variation of theme A under an F# pedal using a 12/16 time signature appears in measure 24.

Longer notes using a 2/4 time with a ternary subdivision follows the initial motif using the diminished scale.
Chromatic notes in measure 27.
We rest on a D dominant chord to prepare an abbreviated repetition at bar 29.
A D# pedal prepares the appearance of a second theme (theme B).

Theme B begins on the last eighth note of measure 31.

The bass presents the theme. It is in B major and uses 2/4 metrics (each eighth note subdivides into three sixteenth notes).
Harmonically the passage uses tonic and dominant chords. Harmony in the right-hand uses the 12/16 time signature.

The theme moves to the upper voice on the last eighth note of measure 39.

We find brief appearances of the pentatonic motif (marked in red) with which the prelude began in bars 42 and 43 transformed by diminution. The sixteenth notes that Debussy has been using as an internal voice are a variation of the motif.
From measure 45, we rest on the tonic. Sometimes with the major seventh, sometimes minor, this tonic chord takes us to section B.