The originality that this enabled -- or rather the complete state of non-hindrance that this created for the originality that existed in Beethoven already -- is the other major source for Beethoven's influence. That is, the innovation that Beethoven created all but necessitated the composer's inordinate influence on the trajectory of Western music; his sound was at once rooted in the technicalities and tones of the last generation of masters, many of whom were Beethoven's instructors, and evocative of the social and industrial revolutions that were occurring throughout Beethoven's lifetime. His harmonies, discords, and turbulence changed the shape of music forever.

There are certainly some scenes of wild passion in music that existed prior to Beethoven, but especially in the generally accepted canon of Western classical music these examples are rather tame in comparison to Beethoven's own work. There is a great deal of restraint, polish, and refinement in the music leading up to Beethoven and subsequent eras, but his ability to escape the sensibilities and mores of the ruling classes -- ironically through their benefice -- enabled him to step away form this polished sound in order to create music that is still amazingly beautiful and yet retains a raw human power and connection with those that hear...

Of course, it is not simply Beethoven's innovations that make him influential, but rather it is the acceptance, use, and adaptation of these innovations by subsequent composers that serves as a marker of this. Near-contemporaries and later composers of the Romantic and later periods take the mixture of Beethiven's beautiful melodies and harmonies with his power and energy to even greater extremes -- the two great Russian composers, Tchaikovsky and Rachmaninoff, stand out as prime examples. Though it would be impossible to trace this trajectory completely and with true certainty, one could even suggest that the raw sounds of much popular music in the twentieth century is the result of Beethoven's innovation.
Beethoven dies before he reached even sixty years of age, and was entirely deaf by that time. He was still composing, however, never having ceased his work. Even in his last days, he continued to envision music that no one had ever been able to imagine before, enabling future composers and musicians to imagine even more in subsequent eras than would have been possible without this musical genius (Lane 2006).

References

Lane, W. (2006). Beethoven: The Immortal. Accessed 22 May 2010. http://www.lucare.com/immortal/index.html