Nocturne in C minor, Op. 48 No. 1 - Chopin (Harmonic analysis of bars 1-16)

Nocturne, Op. 48 by Chopin is in the key of C minor and has the time signature of 4/4 and Lento. Chopin wrote Nocturne in C minor, Op. 48 No. 1 in 1841 for the piano.

In bar 1, the left hand plays the chords I, V, I, VI, with accompanies the right hand playing V and VI whilst the left hand plays the chords G and A.

In bar 2, the  left hand starts on the note of B which is the leading tone, and the right hand plays a G, which is the dominant. The left hand then plays the dominant 7th chord (G7) followed by the tonic (Cm). In the right hand, a short motif is being played around the supertonic of D. This section contrasts against the tonic and dominant pattern that is played in the left hand.

In bar 3, the right hand goes back to the tonic (Cm), whilst the left hand plays the chord of A (submediant), which puts us into the key of Am. The left hand then plays the subdominant, whilst the right hand plays a D. This causes suspension as it resolves to a C whilst the left hand accompanies with the dominant chord of G.

In bar 4, the second beat consists of the inverted dominant 7th chord (F, G and B), which resolves to Cmajor which we can see on the third beat, whilst the right hand plays a neighbouring note around the note of A. 

In bar 5, we have a 2nd inversion diminished Em chord, which is the mediant. This goes to a root position V7 chord in FM, the subdominant. If we look ahead at the next few chords in the LH, which are octaves of Bb, B, and C respectively, it becomes clear that we are moving chromatically up the keys in this section of the piece.

Then in bar 7, the left hand moves up a tone to D, providing a change to the chromaticism. It is clear here that we are in D, because the right hand is playing a motif based around D. Then in the left hand we get Ds and then F and A- a Dm chord. However the F# in the right hand creates a dissonance which resolves to a G in the 3rd beat of the bar and we get a chord of GM.

In bar 9, the left hand descends to Gb followed by F.

In bar 10, the right hand is playing around the submediant (VI) and the subdominant (IV), whilst the left hand chords are: VI-VI-IV-I.

In bar 11, the right hand plays passing notes of A and B between beats 1 and 2, followed by an escape note of C on beat 4.  The left hand plays the chords VII-I-II-III along with the interjections of two dominant 7th chords (V7). The left hand descends back to the tonic and leading tone in bar 12.

In bar 12, the left hand plays the dominant 7th (V7) chord again, and resolves to a 2nd inversion of the tonic chord (Ic).

In bar 13, the left hand plays octaves of F, followed by an F major chord. This then ascends to A, followed by the return of the F major chord. Whilst the is happening, it remains in the chord of F (IV) and stays the same for the next bar.