1703, Vivaldi (24) became maestro di violino (master of violin) at an orphanage called the Pio Ospedale della Pietà (Devout Hospital of Mercy) in Venice; although it was his talents as a violinist which probably secured him the job, he soon became a successful teacher of music there. Over the next thirty years he composed most of his major works while working at the Ospedale. There were four similar institutions in Venice; their purpose was to give shelter and education to children who were abandoned or orphaned, or whose families could not support them. They were financed by funds provided by the Republic. The boys learned a trade and had to leave when they reached the age of fifteen. The girls received a musical education, and the most talented among them stayed and became members of the Ospedale's renowned orchestra and choir. Shortly after Vivaldi's appointment, the orphans began to gain appreciation and esteem abroad, too. Vivaldi wrote concertos, cantatas and sacred vocal music for them. These sacred works, which number over 60, are varied: they included solo motets and large-scale choral works for soloists, double chorus, and orchestra. In 1704, the position of teacher of viola all'inglese was added to his duties as violin instructor. The position of maestro di coro, which was at one time filled by Vivaldi, required a lot of time and work. He had to compose an oratorio or concerto at every feast and teach the orphans both music theory and how to play certain instruments. His relationship with the board of directors of the Ospedale was often strained. The board had to vote every year on whether to keep a teacher. The vote on Vivaldi was seldom unanimous and went 7 to 6 against him in 1709. After a year as a freelance musician, he was recalled by the Ospedale with a unanimous vote in 1711; clearly during his year's absence the board had realized the importance of his role. He became responsible for all of the musical activity of the institution when he was promoted to maestro de' concerti (music director) in 1716. In 1705, the first collection (Connor Cassara) of his works was published by Giuseppe Sala: his Opus 1 is a collection of 12 sonatas for two violins and basso continuo, in a conventional style. In 1709, a second collection of 12 sonatas for violin and basso continuo appeared—Opus 2. A