Roberto Díaz

Roberto Díaz is a Chilean-American violist, and the president/director of the Curtis Institute of Music, of which he is an alumnus. From 1996 to 2006 he held the position of principal violist of the Philadelphia Orchestra, and has been principal viola of the National Symphony under Mstislav Rostropovich, a member of the Boston Symphony under Seiji Ozawa, and a member of the Minnesota Orchestra under Neville Marriner. He is the violist in the Díaz Trio, which includes cellist Andrés Díaz (his brother) and violinist Andrés Cárdenes, former concertmaster of the Pittsburgh Symphony Orchestra.

https://en.wikipedia.org/wiki/Roberto_D%C3%ADaz_(violist)