I’m always excited to hear when something rad is happening in my hometown. Austin’s one of those special places where music, by both general consent and official decree, is a priority. It’s literally what the town has decided to Be About. But I’ve always had the sense that the wild/literate/overachiever/weirdo dimensions were under-represented — though, actually, I probably just wasn’t paying attention. I am now, and I’m kicking myself that I’ll have to miss this ark: The intrepid Austin New Music Co-op have erected Cornelius Cardew’s masterpiece “The Great Learning.” It’s 5+ hours long, spanning two evenings, featuring more than