If you feel the earth tremble beneath your feet starting Thursday Friday afternoon, don’t be alarmed, it’s not an earthquake. It will be the sound of dozens of timpanists vying for the timpani position being vacated by the retiring Paul Salvatore at the end of this season. A timpocalypse! Did you know there are two distinct kinds of timpani? I didn’t until this week. Yes, there are German and American varieties of timpani, and they have different tuning apparatus and set ups (they’re pretty much exact opposites). This means that the orchestra has to supply two sets of timpani for the candidates to audition on, and also two sets for them to warm up on. There will be timpani all over the Arlene this weekend!