The Nocturne in C-sharp minor, referred to as Nocturne No. 7 in the context of the complete set of Chopin's Nocturnes, is initially marked larghetto and is in 4/4 meter, written as common time. It transitions to più mosso (more movement) in measure 58, along with a time signature change to 3/4 meter. The piece returns to its original tempo and meter in measure 93, and ends in an adagio beginning in measure 127. The piece is 134 measures long and written in ternary form with coda; the primary theme is introduced, followed by a secondary theme and a repetition of the first.
The opening alternates between major and minor and uses wide arpeggios, commonly found in other nocturnes as well, in the left hand; such arpeggios require a wide left hand to play smoothly. James Huneker commented that the piece is "a masterpiece" pointing to the "morbid, persistent melody" of the left hand. The più mosso uses mostly triplets in the left-hand and modulates to A♭ major in measure 68. It ends with a cadenza before transitioning back to the primary theme. For David Dubal, the più mosso has a "restless, vehement power". Huneker also likens the più mosso to a work by Beethoven due to the agitated nature of this section. The coda "reminds the listener of Chopin's seemingly inexhaustible prodigality" according to Dubal while Huneker calls it a "surprising climax followed by sunshine" before returning to the opening theme.
