Nocturne Op 9 No.1 in B Flat Minor 夜曲作品9 之1 降 B 小调

One of the better known nocturnes, this piece has a rhythmic freedom that came to characterize Chopin's later work. The left hand has an unbroken sequence of eighth notes in simple arpeggios throughout the entire piece, while the right hand moves with freedom, occasionally in patterns of seven, eleven, twenty, and twenty-two in the form of polyrhythms. The piece is 85 measures long and in 6/4 meter. It is written in ternary form; after the primary theme, the secondary theme starts in measure 19, followed by a modified version of the primary theme in measure 70.

The opening section moves into a contrasting middle section in the same key signature, which flows back to the opening material in a transitional passage where the melody floats above seventeen consecutive bars of D♭ major chords. The reprise of the first section grows out of this, followed by a Picardy third ending.

夜曲Op. 9 No. 1是降B小调，常被香港图书馆列作休馆音乐之用。具有非常自由的旋律，至于其右手部分中出现7、11、20和22连音。全曲的左手部分为一连串由八分音符组成的琶音。

此曲结构为A-B-A，在进入第三乐段前的过渡使用降D大调，并以皮卡第三和弦作为乐曲结尾。