Your comment on Mendelssohn's violin concerto got me really curious. Here it is: http://youtu.be/nO_aRIXXXpE It kicks off with the main theme. Then after the cadenza (around 9:30) the orchestra joins in with the main theme again, that's not variation? Sorry, sorta on and off topic, I know, but I am very curious about this LOL.
I now have homework to do. Having read your description, I will listen to each piece again. Your posts have helped understand them much better. Again, thank you so much! You are awesome.