I do love classical music, don't you? (I'm even more partial to opera, but that's beside the point.)
If you do, too, here's another Christmas-time opportunity in Milan's beautiful Duomo...More......
At 7 P.M., right after the church service, there will be a concert.
The info, available on the Duomo's page in English (yeah!) even contains the music program!
Entrance is free, but--here's one of my soapboxes, again!--if you're visiting the church like a concert hall or a museum, and not to pray, please find and donate generously to the box labelled "restauri"...it's for the church's restoration and maintenance, and the poor Duomo does need a great deal of help in that area.
As long as I'm mentioning it, on the same official website there is information about how to buy contemporary art to favor the Duomo's restoration and how to donate for the restoration of a specific pinnacle.