The Nocturne was originally an ensemble piece meant to be played in the evenings. It was already known in the eighteenth century, but its use here was developed around 1820 by the Irish composer John Field. He is known as the father of the nocturne. Chopins collection of 21 nocturnes is the most famous, and is considered a highlight of piano literature.
As John Field created the genre, a nocturne is a cantabile melody (it can be sung) over an arpeggiated accompaniment. In theory I understand what it means, but I don’t play the piano myself. I find it difficult to recognise these patterns.
Only number 21 is missing. It was not titled a nocturne, but when it was published in 1938 it was called a nocturne just the same. And usually it is included, but not here.
Some years ago I saw Tamás Vásáry, and I must admit he made an impression. The Hungarian pianist and conductor was born in 1933 in Debrecen, and now lives in Switzerland.