When singers/barbershop quartets harmonize a perfect chord, an extra note occurs that sounds like a fifth voice. 2:32 in this video is one of the best I've seen.

https://youtu.be/c8SEVKjIoXk?t=135

Submitted January 29, 2019 at 01:39PM by CrazyIra http://bit.ly/2HClYIz