Here is, in two parts, Alfred Brendel’s performance of the Adagio Sostenuto from Beethoven’s 29th Piano Sonata, opus 106, best known as the “Hammerklavier” sonata. While the sonata is nominally in Bb major, the main tonal center of its ethereal slow movement — this “mother of all nocturnes” — is actually F# minor.
The first video should start at 5’43” in. (“Thanks” to youtube/wordpress.com limitations, you may need to manually wind it there, or open in a new viewer window. Alternatively, click here to hear the audio of the whole piece via GrooveShark.)
The second video should start right from the beginning (it’s actually split at a musically meaningful point, just before the recapitulation of the main theme in varied form):