The Clarinet Concerto was completed less than two months before the composer's death in 1791, and is one of his greatest achievements. Mozart originally intended the work to be for basset horn, but revised it for clarinet. The version that we have come to know and love today actually differs widely from the original. This is because it was written for clarinetist Anton Stadler, who played with an extended bass compass that allowed Stadler to demonstrate his famed ability to play low notes. The piece had to be transposed higher in order to be played on the modern clarinet.