I have to sing/create a song in one of my classes. We can either sing it or use a program to sing it for us. I don't want to sing it but i don't know anything that will sing?

Since it's December and nearing holiday season, why not a familiar holiday / wintry song?

Frosty The Snowman, for ex.
Or make up one with three verses that all end with the same last line so listeners know what's coming: For ex. "Underneath the Christmas tree."