“Chopin composed 21 nocturnes, 18 of which were published during his lifetime,” (The Guardian). “They span almost his entire creative career – the earliest were written in the late 1820s, when the composer was still in his teens, the last in 1846, three years before his death. That period also coincided with massive advances in the technology of the piano itself; the instruments that Beethoven and Schubert wrote for – the kind that Chopin would have known in his youth – were very different in their tonal capabilities and power from those that he was able to play and compose on in the last decade of his life.
In some significant respects, Chopin’s development as a composer, and the steady refinement of his musical language, are inseparable from the increasing expressive power that the steady advancement in piano technology offered him through his career. Together with the mazurkas, the other miniature form that he made his own, the nocturnes provide a musical chronology of that development.”
“Chopin’s Nocturne in G (1839) is written like a barcarolle, a song of the Venetian gondoliers. In the left hand you’ll hear the gentle rocking motion of the boat,” (VermontPublic.org). “The music shifts and the key changes just like the scenery passing by. The boat comes to a rest and we hear a melody, like the gondolier singing a simple, repetitive song.”
After the piece begins in G major, at the 0:18 mark we’ve clearly launched into new harmonic territory, with many additional shifts throughout. However, the piece manages to come to its final resting point by returning to the key of G major.