Giovanni Battista Morsolino (c. 1540-1591) was an Italian organist and composer. He had an active international career serving at the Bavarian Court in Munich, at Santa Maria Maggiore in Bergamo and in Milan cathedral (Duomo). Firstly, this work traces Morsolino’s biography focusing on the period spent in Milan (1590-1591). Secondly, making the point about a variety of unpublished sources as regards liturgy, organists, and organs in Milanese Duomo, it delineates the extensive context in which Morsolino worked (c. 1560-1650).