a nocturne is music to be played at, or that is evocative of, night. Chopin's sets are easily the best in the genre. why? well there's very little overt complexity here: the form is a simple ABA, with two contrasting themes; the (mostly) uncomplicated harmony is supplied economically by arpeggiated chords in the left hand. you've probably come up with more complicated melodies singing to yourself in the shower. so what makes these so fucking excellent, then? the eastern-European lilt also heard in Bartok, Rach., and Scriabin? the impressionistic tone colors of Debussy, Ravel, and Gershwin? hell if i know. Rubinstein said "Chopin was a genius of universal appeal... [His music] does not tell stories or paint pictures. It is expressive and personal, but still a pure art. Even in this abstract atomic age, where emotion is not fashionable, Chopin endures. His music is the universal language of human communication. When I play Chopin I know I speak directly to the hearts of people." well shit then.
a note on the recordings: Rubinstein's collection is the best available. he plays it the way i think Chopin would, with delicacy and impeccable phrasing that shapes the melodies and emphasizes interesting harmonies. Ashkenazy's interpretation is more dramatic, with lots of exaggerations in tempi and contour. it makes for an uneven set (he absolutely butchers the Bb min.), but his highs are probably higher than Rube's, especially where power and flair are concerned (F, Ab). also included is a mix of modern-ish nocturnes and ephemera influenced by Chopin that you might also like (parent discs available if you ask nice).
Rubinstein disc 1
Rubinstein disc 2
Ashkenazy disc 1
Ashkenazy disc 2