Although the exact events are not documented, scholars have inferred that Boyleau probably spent his first Italian years in Venice, due to musical influences seen in his work as well as their publication history.
In 1551 he became maestro di cappella (choirmaster) at Milan Cathedral, his earliest documented post; he held this position until 1557, at which time he was replaced by Hoste da Reggio.
In 1572 Milan Cathedral hired him again, first as assistant to Vincenzo Ruffo, and then as maestro di cappella, the job he had left (or been dismissed from) fifteen years before.
[1] His sacred music was conservative and tended to be modest, as could be expected for a musician working in Milan, the home of Cardinal Carlo Borromeo, the principal force behind the musical reforms during the Council of Trent (complex polyphony, unclarity of diction, and "immodesty" were among the qualities for which contemporary musicians were criticized by the Council).
He wrote a book of motets which he dedicated to Giovanni da Legge, the procurator at St. Mark's in Venice in 1544; he may have been seeking a job there, the most prestigious musical institution in northern Italy.