“About midway through a night of contemporary works, John Eichenseer, who goes by the name JHNO, was performing his Untitled, a new piece for viola and electronics, when he heard hissing, then an outburst of clapping intended to disrupt his playing, then another.” The heckler turned out to be “Bernard M. Zaslav, a viola player with a pedigree as a champion of contemporary music.”