As every musician knows, John Field invented the Nocturne, and by doing so earned for himself his small but secure niche in music's Pantheon. The word Nocturne was not entirely new to music. Haydn, Mozart, and many lesser composers had used its Italian or German equivalents for vocal and instrumental works intended for performance at night. But the notturni and Nachtmusiken of the eighteenth century have little in common with the wordless love-songs which Field called Nocturnes. His invention was something more important than an evocative title; it was the crystallization of an idiom, and through this idiom a new aspect of the romantic movement could be channelled into the mainstream of music.