Clarinet Concerto in A major, K. 622

Mozart completed the Clarinet Concerto in October 1791, weeks before his death, for Anton Stadler, whose low register he had already written for in the Quintet K. 581. The work began as a concerto in G for basset horn, K. 621b; Mozart transposed the surviving material and finished it for Stadler's basset clarinet, an instrument extended downwards by four semitones. Those low notes were smoothed away in the first printed editions, so the version played for well over a century was an editorial reconstruction; performances today often restore the original compass.