There are some multi-track barbershop videos on Youtube which are good examples of over-the-top overtones. The fact that it's the same person (with the same tim

There are some multi-track barbershop videos on Youtube which are good examples of over-the-top overtones. The fact that it's the same person (with the same timbre, "overtone profile") doing all the voices seems to amplify the effect. Here's one: http://www.youtube.com/watch?v=QpU_X6VKqvA http://www.youtube.com/watch?v=QpU_X6VKqvA