In April 1787, Mozart wrote a letter to his ailing father in which he described death as humanity’s “true best friend … the key to our true happiness.” We hear that sanguine attitude in this serene and luminous Quintet in C Major, written during that same period, which concludes in an atmosphere of unfettered ebullience. Scored for string quartet and an extra viola (like all six of Mozart’s quintets), it abounds with typically Mozartian nuances that would later inspire Schubert—especially in the slow movement, a veritably operatic duet between the viola and the first violin.