Several years ago, I began working with combining well-known melodies and treating them with non-traditional harmonies. "Silent Night" by Franz Gruber and "Away in the Manger" by James Murray are two of the best examples I have enjoyed working with. These "cradle songs" combine easily, and because the are so well known, you can follow both at the same time. Let the melodies dominate, using the harmony for color with a tempo that allows the band to flow from one phrase to another. Begin and end the piece as intended, elegantly simple.