German bassoonist and pedagogue Julius Weissenborn is known primarily as an author and composer of method and etude books familiar to all bassoonists. However, he also composed a number of solo works, including a collection of pieces in his Opus 9, for bassoon and piano.
The first two works of this opus, Arioso and Humoreske, pair so well together that they are often performed together as a single piece, something slow and lyrical, followed by something quicker and technical. And it just so turns out that with a relatively simple transposition, they are perfectly suited for the bass clarinet. In this edition, for each movement, the piano part has been transposed down a whole-step to better accommodate the bass clarinet.