A friend turned me on to the Goat Rodeo Sessions, and I'm completely on board. It's Yo-Yo Ma and three other stringed instrument virtuosos that don't quite make up a quartet (with a special guest singer on one song):
Yo-Yo Ma, Edgar Meyer, Chris Thile And Stuart Duncan: NPR Music Tiny Desk Concert - YouTube
Edit: yowza, large embedded video is large. Spoilered.