The Op.42 Notturno for Viola and Piano is an arrangement of the 1796-97 Serenade in D, Op.8, arranged by F. X. Kleinheinz (with Beethoven's approval) for Viola and Piano. The piece is comprised of seven short movements. The first is a simple march, while the second is an Adagio. The ensuing minuet is attractive and proves to be an interlude between two Adagios, of which the second alternates effectively with a contrasting Allegro molto Scherzo section. There follows an attractive Polonaise and a theme-and-variations marked Andante. A reprise of the opening march concludes the work. Overall, it is a delightful minor composition in Beethoven's vast output.