The painting representing the Madonna and Child, St Mark, St Augustin and the kneeling Agostino Barbarigo, and musician angels is known as the Barbarigo Altarpiece. It was commissioned by a member of the Venitian aristocracy Agostino Barbarigo, the painting originally hung in the family palace. When he died in 1501 it was left to the women's monastery of Santa Maria degli Angeli at Murano.
Later however it was moved to the present location of San Pietro Martire, Murano to make room for a painting by Titian (since lost).
information courtesy of the WGA