On Sunday, I withstood a few minutes of Dan Gilsdorf’s Diabolus in Musica, watching singers in an outward-facing circle, each humming one note to maintain a single chord. As the serious singers ignored the viewers from close range, like Buckingham Palace guards, I basked in the heady dissonance. If (as 18th-century Catholicism contended) that chord is wrong, I don’t wanna be right. Even more...