At first, Philip Glass’ minimalism made him such an outlier, the composer resigned himself to being the principal performer of his compositions. That resulted in iconic first takes, but Glass’ canonization now allows us the chance to hear other interpretations. Bruce Brubaker’s look at famed Glass piano pieces (“Mad Rush” and most of “Metamorphosis”) offers more delicacy and a less propulsive approach, but his powerful shifts in volume can notch a big impact. And his version of “Wichita Vortex Sutra” has the prophetic, incantatory dynamism of the Allen Ginsberg poem that originally inspired Glass.