Tuesday-Thursday: In 2006 a young, ambitious group called Brooklyn Rider founded this festival as a platform for its uniquely inventive approach to the string quartet format. This year's festival is, sadly, the last — the New York-based, Minnesota-rooted quartet has simply become too busy to curate it properly. The farewell concert is a beauty, though, with eminent Swedish mezzo Anne Sofie von Otter joining the quartet in a typically exciting program of new commissions and arrangements. (7.30 p.m. Thu., Trinity Lutheran Church, 115 N. 4th St., Stillwater; $10-$25, ­ The festival opens with a champagne recital of Brooklyn Rider highlights. (7:30 p.m. Tue., Washington County Historic Courthouse, 101 W. Pine St. Stillwater; $10-$25.) And there's also a free, hourlong family concert. (6:30 p.m. Wed., Stillwater Public Library, 224 3rd St. N.)

Terry Blain