There is nothing quite the same as the sound of a REALLY good barbershop quartet (or chorus) locking onto a chord---especially in person. I hope the quartet DOES go on with it! If they don't already, they should look into joining the Barbershop Harmony Society if there's a local chapter.
Full disclosure: My dad and uncle were both barbershoppers when I was little. I fell in love with four-part harmony then, and I STILL love good barbershop. I have recordings, but I haven't heard live barbershop for too long. In the 1990s my dad and uncle sang with two other guys as the Glade-Tones. (They weren't very good, but they were barbershop!)
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We once had a 16mm film print of "The Music Man," but we finally sold it in favor of watching the DVD---because the 16mm print wasn't in wide-screen format, it bothered me that I couldn't see all four of the Buffalo Bills onscreen! One of them was always cropped out in the 4:3 format.
Your dad & uncle were great! I'd love to be able sing like that!