Nice job!  I particularly enjoyed the history you provided about the keyboard instruments.  I never really thought about it, but I always assumed that pianos were always a part of orchestras and musical compositions.

You included this quote, "but by the time Vivaldi finished the more than 500 concertos attributed to him a standard form had emerged that many other composers would imitate.”  Do you think that Vivaldi *knew* he was creating a standard, or is that something that just happened?