Originally Posted by wikipedia

The first major innovations in the development of the solo concerto were made by Antonio Vivaldi, who established the ritornello form: solo passages alternate with orchestral tutti, which often repeat the same material, giving unity to the movement. He established the three-movement form (fast–slow–fast) which has been the norm for the solo concerto ever since. He wrote several hundred concertos, the most famous being the group of four for violin entitled The Four Seasons. His 12 Concerti, Op. 3 "L'estro armonico" are also arguably the most influential pieces of the first half of the Eighteenth Century.