Schubert String Quintet, D. 956 The String Quintet in C major, D. 956 - and often referred to as Op. posth. 163- was Franz Schubert's final chamber work. It is a cello quintet, in the sense that it is scored for a standard string quartet lineup plus an additional cello -with the viola being by far the most common choice. The work has been described as a chamber music masterpiece, and since its public performance in 1850 and its publication in 1853, it has gained status as one of Schubert's finest works.