Peter Serkin, a pianist who navigated a distinctive course through classical music with thoughtful interpretations of both standard repertoire and bracing new compositions, died Saturday morning at his home in Red Hook, N.Y. at age 72. The cause of death, announced by his family, was pancreatic cancer. Serkin came from a prestigious family of musicians. His father, the celebrated pianist Rudolf Serkin, and his maternal grandfather, the violinist and conductor Adolf Busch, embodied old-world traditions — to reverential acclaim. But Serkin crafted a singularly new-world approach to his classical career. In his early 20s, disillusioned with the pressures of lineage and tradition, Serkin dropped out from performing altogether, traveling to Asia and listening to albums by the Grateful Dead . After he returned, Serkin co-founded the chamber group Tashi in 1973 (with cellist Fred Sherry, violinist Ida Kavafian and clarinetist Richard Stoltzman), which championed new music and often performed