How far back in time does experimental music go? To 1913 and Luigi Russolo with his Art of Noises? To the 1920s and Edgard Varese with his dissonant symphonies? To the 1940s and John Cage with his prepared piano? To the 1950s and France’s musique concrete vs. Germany’s electronic music? Despite the fact that experimental music had been around for decades by the time the 1960s arrived, the time was still ripe for the kind of highly unusual artistic invention that could incite amazement, confusion, deep contemplation, surprise, revelation, laughter, or anger. Enter the ONCE Festival, which delivered all of that and much more.