Some friends complete us, while others complicate us. Maybe you feel as if there were nothing better in the world than driving in a car, listening to music with friends, looking for an all-night donut shop. Nobody says a thing, and it is perfect. Maybe your lifelong fascination with harmony finally began to make sense in those scenes, packed in your family's station wagon, singing along to "God Only Knows," waiting in the parking lot until the song was over.