Beethoven was a revolutionary composer as shown by his 3rd, 5th and 9th symphonies, late string quartets and other works. So if he had not been born, would another composer, who lived in OTL, have been as revolutionary? Would there have been the same major change in the symphony, and would another OTL composer have composed a choral symphony? I am assuming that the butterflies do not extend beyond the people he knew in his life.
If I remember rightly, I have read that Brahms was greatly influenced in his music by Beethoven.