The Pietà was one of four Venetian ospedali, each with a different function: the Mendicanti housed the poor, the homeless, beggars, war wounded etc.; the Ospedaletto was a home for orphans; the Incurabili housed those with incurable diseases; the Pietà was a home for abandoned and unwanted babies, not (as is often stated) a convent or a school for girls.

Babies were brought in for various reasons, some found by the roadside or floating in the canals, perhaps from families too poor to bring them up, or whose mothers had no milk, but most were children born through prostitution. They were placed in foster homes for the first six years, and then returned to the Pietà. The boys learned a trade such as stone cutting, weaving or shoe making, and left equipped with a skill at the age of 16. The girls had three options: to marry, to become nuns, or to stay at the Pietà for the rest of their lives.

There were two groups of women, the Figlie di Comun (non–musicians), who did the sewing, embroidery, silk and cotton weaving, took care of various tasks in the institution and sold some of the work they produced, and the Figlie di Choro (musicians), the élite of the Pietà, some 60–70 in Vivaldi’s day, who had separate rooms and a special diet.  A privileged few were allowed to earn extra income by teaching the daughters of wealthy families sent to the Pietà as Figlie in Educazione. The two senior musicians were known as maestra, and the head of the household was the priora. The skills of the "choro" attracted visitors from across Europe and a visit to the Pietà became a feature of the Grand Tour. Vivaldi’s job was to train those girls who showed musical promise (about one in ten) to sing and play instruments during services at La Pietà. He wrote many works for this establishment, and evidence suggests that all the vocal parts were sung by women, including tenor and bass. He started his career at the Pietà as Maestro di Violin in September 1703, aged 25, six months after being ordained a priest. In 1714 he was invited to succeed Francesco Gasparini as Maestro di Choro, but refused the post; a short time later, however, he was appointed to the specially created office of Maestro dei Concerti.  During this period he wrote his first sacred works, including the well–known Gloria.