Ambrosian chant is the specific style of singing associated with the church in Milan; it is related to, but independent of, Gregorian chant. Legend ascribes the creation of Ambrosian chant to Milanese bishop Saint Ambrose and cites 13 chants believed to have been written by him. However, there are no known manuscripts of Ambrosian chant that predate the twelfth century, making its traditional claim of being the "world's oldest continuously active repertory" a little unsteady. Nonetheless, recordings of Ambrosian chant aren't exactly thick on the ground, especially as compared to Gregorian chant. A great place to start is with this disc, Ambrosian Chant, by the female vocal group In Dulci Jubilo as led by musicologist
Alberto Turco. The singing throughout is magnificent, and as the Ambrosian melodies are largely bright and diatonic in nature, the use here of women's voices brings out a shimmering, sunny quality that illuminates the chant and avoids the sense of stasis common to many more typical chant recordings. If you are looking for something different and refreshing in terms of chant, this Naxos disc Ambrosian Chant is an item you wouldn't want to miss. It may well also appeal to those who enjoy the group
Anonymous 4 or the works of medieval composer Hildegard of Bingen.