The Nocturne in B flat minor is sombre and plaintive, though Chopin ends the piece in major mode. The middle section is the most original: a melody presented in octaves with startling and rapid changes of harmony. It builds up to a pedal point (shadows of Bach) where for sixteen bars the harmony stays in D flat major, then chromatically returns to the tonic key. Sonority is of crucial importance here.
from notes by Angela Hewitt © 2004