Chopin’s favourite of these four pieces was the Impromptu in G flat major, Op 51
(1842). It begins rather like the first of the set with triplets in both hands, but is harmonically more adventurous. The ascending scale which appears initially in bar 9 makes our spirits soar. The middle section, however, is what makes this piece very special. The left hand must sing like a cello and capture something of the darkness of the key (E flat minor) while the right hand accentuates the restlessness beneath the surface.
from notes by Angela Hewitt © 2004