If there's one thing Raffi understands, it's that music can be used to edify. But that mission doesn't bog down his tracks; rather, he comes up with delightful new takes on traditional themes. “Five Little Frogs” and “Five Little Pumpkins” find him counting with a cappella panache; in his world, “Old MacDonald Had a Band,” where kids are introduced to instruments through the wacky sounds they make.