It is in ternary form:

A [a (measures 1-8) + a1 (measures 9-21)]

B [b (measures 22-30) + b1 (measures 31-38)]

A1 [a2 (measures 39-44) + Coda (measures 45-55)]

The main key is C major. The opening eight measures are in C major, followed by a repetition of the same melody in the parallel minor (C minor), leading to a half cadence. In the middle section B, the music develops in A minor, the relative minor of the main key. From measure 23, the melody begins with the dominant chord of A minor. The left hand, with its raised 6th scale degree (F#) characteristic of the melodic minor scale, contributes to a brighter feel; however, when the note C appears in the right hand at measure 25, the key of A minor becomes clearly established. From measure 31, the roles are reversed, with the left hand taking over the melody.

Measure 37 is the dominant chord in A minor, while measure 38 is a double dominant for A minor, and a dominant of the mediant (III) for C major (a dominant of the mediant typically leads to a deceptive cadence by progressing to the tonic I). It functions as both a departure chord and an arrival chord.

The four measures from measure 39 feel like a condensed version of sections 'a' and 'a1' from the A section, rapidly shifting between C major → C minor → C major within two measures. Here, rather than perceiving it as a change of key, one should express it as a contrast of light and shadow. The Coda is a descending sequence, but due to the accelerando, it should be expressed rhythmically and with a sense of urgency, focusing on the repeated figures rather than subtle harmonic nuances.