He often thought, If Beethoven or Chopin had centuries to compose music, imagine the treasures we would have.
The development of pianoforte technique since Beethoven has been in some ways even more revolutionizing than that of the brass instruments; and pianoforte instrumentation, both in solo and in chamber-music, is a study for a lifetime.
Beethoven almost always has 2 flutes, and invariably 2 clarinets.
Similar principles apply in infinite detail to the treatment of wind instruments, and we must never lose sight of them in speculating as to the reasons why the genius of Beethoven was able to carry instrumentation into worlds of which Haydn and Mozart never dreamt, or why, having gone so far, it left anything unexplored.
Magnificent examples are Mozart's trio for pianoforte, clarinet and viola, his quintet for pianoforte, oboe, clarinet, horn and bassoon (imitated by Beethoven), his quintet for clarinet and strings, Brahms's clarinet-quintet for the same combination, and his trio for pianoforte, violin and horn.