In classical times and for much of the 19th century, piano trios were sort of fashion items. It is therefore not surprising that after Haydn and Mozart, Beethoven also tried this genre and left a total of 13 piano trios.
The works contained in this volume III almost all have small peculiarities: op. 44 is not a trio in its own right, but consists of a single movement of variations, the WoO 37 was written while Beethoven was still in Bonn and distinguished by its instrumentation (piano, flute and bassoon), the WoO 39 was written for little Maximiliane, daughter of the Brentano family "to encourage her to play the piano", op. 38 is an adaptation for piano, clarinet and cello of the septet op. 20, and the last piece reached posterity only in the form appearing in the sketchbook used by Beethoven when he was in Bonn. None of these works have the scale of his great piano trios, but they nevertheless remain witnesses to his great art.