The Klein Four is the premier a cappella and variety group in the world of higher mathematics. We call the Mathematics Department of Northwestern University our home. You might remember us as the group who brought you "Finite Simple Group (of Order Two)." Since then we've recorded a CD, Musical Fruitcake, available on our website as well as through iTunes, Napster, Rhapsody, MSN, and other digital services. We are also video stars... as long as radio doesn't kill us.