In 1796, Beethoven wrote four pieces for piano and mandolin—Sonatina WoO. 43a, an Adagio in E flat, WoO. 43b, and a Sonatina and Andante con Variazioni for piano & mandolin in D major, WoO. 44a and WoO. 44b, respectively. It appears that all four pieces were composed for the Countess Josephine de Clary. She would later become Countess von Clam-Gallas, and it would be in the library of her husband that the manuscripts of these four unusual works would be found.
This WoO. 43a Sonatina is a minor composition by the composer. It is delightful and colorful in its lightness, and, for its instrumentation, it is certainly a worthwhile effort. WoO 44a is a single-movement rondo. The mandolin leads a dashing rondo theme, pausing for breath only in the contrasting episodes. If you didn't know any better you'd think you were listening to bluegrass. The harpsichord or piano accompanies throughout, occasionally imitating a phrase of the mandolin's.
Here's a good selection I 'plucked' out of the YT ether...
1. WoO 43b - Adagio ma non troppo (Live)
2. WoO.44a - Sonatina in C (Rondo) (Live)
3. "The Ruins of Athens" mandolin duet (RANIERI "L'Art de la Mandoline") (Live)
4. WoO.43a - Sonatina in Cm
5. WoO.44b - Andante con variazioni in D