nocturne

noun2

1. •
   A work in a genre of piano music of moderate tempo with a highly-decorated, improvisatory melody.

   • The vocal nocturne, in other words, turns out to be no easier a genre to define than the piano nocturne. But its ambiguities are nevertheless helpful in making sense of those of the piano nocturne. — 2004
2. •
   A work of art relating or dedicated to the night.