"my favourite nocturne by Monsieur Field"
(1782-1837) was an Irish composer famous for having invented the nocturne for the piano. He lived and worked in Russia for much of his life, attracted by the artistic atmosphere of St Petersburg. Field is at the height of his fame and his creative life when Countess Rostova talks about him.
Listen to John Field's Nocturne No. 1 in E flat Major on Spotify.