He was born in Brescia, to a family of prolific organ builders,[1] a profession which also included his father Graziadio.
At age 21, he was sent by his father, who reassured the Duke Guglielmo Gonzaga of his son's abilities, to fix the organ of the basilica of Santa Barbara in Mantua.
Additionally, Costanzo worked with his father in the construction of the Antegnati organ, at one time the largest and most famous in the world, which was built in 1581 for the friars of St. Joseph's Church in Brescia.
[3] Although few of his instruments survive, the remarkable Organ Antegnati of the church of St. Nicholas (1588) in Bergamo was restored in 1996.
Subsequently, he published, on an almost biennial basis, anthologies of mainly sacred compositions (Masses, psalms and motets), but also including secular works.