4[a] is a composition for flute and keyboard attributed to Ludwig van Beethoven found amongst his papers after his death.
Following Beethoven's death, a number of unpublished works were discovered amongst his papers including the Piano Trio, WoO.
[1] Alexander Thayer noted that when the sonata was discovered, the manuscript was not in Beethoven's handwriting, making attribution to the composer problematic.
[2] Musicologist Willy Hess argued that Beethoven would not have retained the work in his papers unless he had some personal connection with the composition.
She also speculated based on the writing for the flute that the work may have been a transcription of a violin sonata.