"The Oldest Established" from Guys and Dolls is really hard to perform the first time. My high school just performed that musical, and I was one of the crapshooters. It is sooo hard, because, like "Fraction" you have to act while you're doing it, and the tenor line is insanely high to sing after you've just been jumping around the stage and carrying a guy on your shoulders. I think musical theater composers purposely write music like that to give the performers a workout
