https://www.youtube.com/watch?v=ZVbJBgOBHk8
Black Square String Quartet recently recorded SÉRAPHÎTA by Trey Spruance. This is an incredible piece. I love the altered intonation. As Trey is a complete genius I will not attempt to explain it here. Rather you should check out his explanation via the Kronos Quartet website: http://50ftf.kronosquartet.org/composers/trey-spruance