I disagree. Beethoven's 5th Symphony doesn't fall into any of those.<p>1) Definitely not the "next obvious step."<p>2) The theoretical principles of canons and fugues, etc. were all in place in the 18th century, but no one but Beethoven could have made the 5th symphony, or anything close to it.<p>3) Obviously, nothing to do with infeasibility.<p>4) Again, not luminary, because no one would ever have though of it. Contemporary musical style would change, and Beethoven's work would never exist.<p>P.S. And if anyone dare try to say the 5th Symphony wasn't an idea, it's brought a lot more good, happiness (relaxation, concerts, etc.), and wealth (selling records, etc.) than most startup ideas...