There are a lot of opinions on the proper way to perform Beethoven’s 9th Symphony, especially when it comes to tempo. Recordings of the piece often differ in length by several minutes, in fact. But it’s a fair bet that Beethoven never conceived of a performance of his groundbreaking work that would last 24 hours, take place in a grimy bar beneath one of Vienna’s great concert halls, and play to an ever-revolving sequence of curious listeners who stop in to catch a few beats before moving on. Grotesque? Maybe. But Mark Swed says that the experience was well worth it.