The Frog Choir run regular performances on the small stage up near Hogwarts in Hogsmeade. They are a mixture of singing students and deep sounding frogs. Think Pitch Perfect with amphibians.
The choir now sing Christmas songs with the frogs backing up the great singing talents of the Hogwarts students. They sing more traditional Wizarding festive songs like Christmas at Hogwarts and I Cast A Spell On Father Christmas. I really enjoyed their version of the traditional carol, We Wish You A Merry Christmas.
You can catch it about 5 times a day over at Islands of Adventure. It's a nice short show that does get you in the Christmas spirit.