Yep yep. The interesting thing about the Barbershop 7th is that it doesn't function like a dominant 7th chord, which feels unstable and pulls towards the relat

Yep yep. The interesting thing about the Barbershop 7th is that it doesn't function like a dominant 7th chord, which feels unstable and pulls towards the relative tonic chord (e.g. G7 -> C). The Barbershop 7th chord has a slightly flattened 7th to line it up with the overtones of the root note, blending it in and making it stable. You might say it's a microtonal effect in that you hypothetically could notate and sing a C7 differently depending on its function in the piece. I don't know whether this is done in practice, though.