From his early ‘teens’, the wind instrument which most deeply engaged Mozart’s enthusiasm was the clarinet. But this enthusiasm was not to be completely fulfilled until the last seven years or so of his life, the time when he enjoyed the inspiring friendship of Anton Stadler, a clarinettist of genius for whom he composed some superb music, culminating in the Quintet, K581, and Concerto, K622, which stand high among the masterpieces of his last years. Besides their intrinsic qualities, these two works have a peculiar historical significance in that Stadler made a notable contribution to the instrument’s technical development which in turn had some influence on the style of the music.