All of the nocturnes are great pieces of work, ranging across many styles. The first notturno could be best described as melancholic. It's evocative, it's sentimental, and it has the rhythmic freedom that became characteristic of Chopin's later work. The third notturno alternates between a nostalgic main theme and a dramatic second theme. They're both very delicate and require a certain amount of virtuosity.

The second notturno is also imbued with melancholy. It's the most celebrated of the three, owing its critical acclaim to its simplicity and pensive nature. It has two repeating themes and a coda. The themes get more ornamented with each appearance. As the song progresses, it sways with rhythmic freedom, as indicated by the words senza tempo or without tempo. It has a contemplative aura until it suddenly becomes vehement near the end with the appearance of forceful octaves. It reaches its climax at the marked fortissimo (meaning very loud). After a thrill-like passage, the agitation gently descends into a harmonious ending.

Nocturne Op. 9, No. 2: opening bars and main theme

There is absolutely no living person that can resist the delicate themes of the deuxième nocturne. The virtuoso hands of the dilettante Arthur Rubinstein simply makes it more irresistible. This particular interpretation straight up melts into your ears, similar as to your consciousness melting into a dream when you're about to fall asleep.

Specifications

The Nocturnes, Op. 9 are a set of three nocturnes written by Chopin. The work was published in 1833.

1. Nocturne in B-flat minor, Op. 9, No. 1 - Larghetto (Rather broadly)
2. Nocturne in E-flat major, Op. 9, No. 2 - Andante (At a walking pace)
3. Nocturne in B major, Op. 9, No. 3 - Allegretto scherzando (Moderately fast) - Agitato (Agitated)

http://en.wikipedia.org/wiki/Nocturnes,_Op._9_(Chopin)