Vivaldi wrote more than 400 concertos for various instruments, especially for the violin. The scores of 21 of his operas, including his first and last, are still intact. His most popular work is the group of four violin concertos called “The Four Seasons”. Each concerto describes a season: Spring, Summer, Autumn, and Winter. He is believed to be the inventor of the ritornello form. He was very famous for his piccolo compositions, such as "Il gardellino".