From its debut performance in Venice, in the 1720s, this expressive and sophisticated music received incomparable international acclaim. Antonio Vivaldi was its best ambassador; as a virtuoso violinist, he delivered the quintessence of his art only when performing for an audience. One of the keys to the work's popularity is its program defined by four sonnets. The Four Seasons are unique in being program concertos; that is, they suggest a series of events. The Seasons are a literary narrative expressed in music, a sort of natural opera theater, in which the soloists are no longer the heroes of antiquity, but simple beings like animals or wine-makers; natural elements or dreamlike realms. The success of the four concertos, however, eclipsed the rest of Vivaldi's work. It took two centuries to realize the brilliance and diversity of his other compositions.