There are a few different works called Ständchen or Serenade. This one is no.4 from a collection of songs D.957 published shortly after the death of their composer Franz Schubert and called Schwanengesang (or Swan Song) by the publisher. The song is a popular one and readily lends itself to being played as an instrumental by various instruments accompanied like the original song by piano. The music illustrated on this page is shown for flute and piano but an oboe or violin (and other instruments) can also play the flute part. Other alternative parts for other instruments are included in the left-hand menu (as are the midi and mp3 file), though note that other instruments in the same key using the same clef and with a similar range can also use these parts. Of particular note is the Cello part with additional pizzicato chords from an arrangement by the composer and cellist Georg Goltermann. Below is a video of the music with a "piano roll" animation, or below that you can play the mp3 file and see the sheet music before downloading. For singers here is the Original Song, an arrangement for Piano Solo, and for guitar players here is a Guitar arrangement by Mertz.
Here is a video of Schubert's Ständchen (Serenade) for flute and piano:
The audio controls below allow you to play the mp3 version of Schubert's Ständchen (Serenade) for flute and piano. Alternatively you can download the music as an MP3 file or as a Midi file.
The image below is the first page of the sheet music, and here you can download the full sheet music for Schubert's Ständchen (Serenade) for flute and piano in PDF format.