There may be no more melodically perfect piece of music from the classical period than Mozart’s quintet for clarinet and strings, K. 581. Playing on modern instruments, clarinetist Jörg Widmann and the Arcanto string quartet offer a limpid and lovely performance of that work, alongside an equally fine rendition of Mozart’s string quartet K. 421, written a few years earlier. Interestingly, it’s the quartet that sounds more Romantic in style than the clarinet quintet, but both are wonderful.