The cappella musicale at Santa Maria presso San Celso in Milan, also known as the church of the ‘Madonna of Miracles’, was originally charged with the performance of individual plainchant Masses on specified feasts, Vespers as a choir daily in the summer and on those specified feasts, and Compline as a choir during Lent. In 1535, however, its duties were expanded to include a High Mass and a Vespers service on the first Sunday of each month. With Carlo Borromeo's ascension to the seat of archbishop of Milan in 1560, the cappella's Vespers service became central to public worship, and attracted foreign visitors as well as the Milanese aristocracy. As a result, public worship services featuring the cappella were expanded to include a Compline service on Saturday evenings. Simon Boyleau, the first documented maestro di cappella at Santa Maria presso San Celso, was a madrigalist familiar to the Milanese aristocracy. His compositions for Santa Maria presso San Celso reflect not only Borromeo's attempts to shape the Milanese liturgical style according to Tridentine aims, but also Borromeo's desire to spiritualize and theologically educate the Milanese aristocracy. Boyleau's tenure at Santa Maria presso San Celso, which featured the cultivation of sacred and secular audiences alike, defined the activities of the church's composers for the next 50 years.