Publisher Desc.  In the central part of the concerto, the Adagio, Mozart's preoccupation with cantabile melody opens a new world of sonority.It opens with a melody which must be one of the most beautiful ever written, sung immediately by the solo clarinet without any orchestral introduction. The more the solo part embellishes, expands, seeming to sprout leaves and tendrils, the more organically the melody seems to grow out of the clarinet tone.