CANCELLED: The musician and composer Terry Riley’s influence stretches farther afield than almost any other figure in 20th-century classical music. His landmark composition, “In C,” first performed in 1964 by an ensemble including Steve Reich, Pauline Oliveros and Morton Subotnick, helped put Minimalism on the musical map, though he now disdains that term. The universal appeal of “In C” extends from its repetitive structure. “If you look at world cultures, repetition was a traditional way of establishing some kind of ecstasy: By repeating something, people would change their mental and spiritual outlook,” Riley said. His preferred partner of the last 20 years has been his son Gyan, a conservatory-trained classical guitarist; the two will perform together two concerts at Pardon, To Tu.