These amazing ladies (http://www.martiniquartet.com/) are both incredibly talented and incredibly gracious. They demonstrated and discussed how to "sing your part smart" and even their attempts to demonstrate "what NOT to do" were still lovely.
They inspired everyone who heard them to continue working, learning, and refining their barbershop skills. They have a gentle touch that can quiet a room in a heartbeat and then they build to crescendos that seem to expand in every dimension without ever being aggressive or brash.
...and no matter where you are on the quartet journey, it's a thrill to see what the human voice is capable of!