We’re all entitled to our obsessions, so long as they aren’t hurting anyone else. And there’s probably no way that the marimba could do any harm. In fact, to Nancy Zeltsman it’s just the opposite, so much so that she spends her life teaching, performing and educating the world about the ancient folk instrument — which, by the way, is still the national instrument of Guatemala. “No party is complete without it,” she notes. Chair of the percussion department at the Boston Conservatory and professor of marimba at Berklee College of Music, Zeltsman has been lauded for her “imagination, interpretation, color, sensitivity and artistry,” all of which are in full evidence at the Zeltsman Marimba Festival. The event, an annual intensive two-week seminar co-sponsored by the Colburn School, features performers from across the globe. Festivities wind up this weekend with legendary mallet percussionist Emil Richards delivering up an evening of jazz on the marimba, and, of course, the awe-inspiring Participants’ Marathon Concert. That’s five hours of marimba and other percussion music in genres ranging from classical and folk to jazz or whatever else can be pounded out with mallets, sticks and other friendly weaponry. There’s obviously some truth to composer-guitarist Steve Mackey’s observation that “these days, you can’t throw a dead cat without hitting a marimba concert.” Colburn School, Zipper Hall, 200 S. Grand Ave., dwntwn.; Emil Richards takes place Fri., July 18, 8 p.m.; Marathon Concert takes place Sat., July 19, noon-5 p.m.; free but $2 donation suggested. Note: “Come and go as you please.” (231) 621-2200, www.zmf.us/ticketchart.cfm.