The challenge for variety

One of the difficulties that even great composers faced was making their music sound different. Music from a given period sometimes runs together. Bach is Bach, and sometimes one piece sounds about like another. Same with Mozart. Even modern composers such as Shostakovich, who were not confined nearly as much by convention, ended up sounding very much alike from one piece to another. Obviously, this was not universally true, but it was from time to time. As someone once pointed out, even the great composers had to eat, and so even Beethoven cranked out a lot of music that was somewhat less than great.