Country star Kathy Mattea has spent recent years experimenting with Celtic music and exploring her folk-music heritage, but one thing has remained constant in her 20-year career: her talent for performing well-written songs. Mattea's latest project is an acoustic, "roots-oriented" tribute to the music of the coal-mining era a century ago and to those who have worked in the mines. Mattea takes the stage at 8 p.m. Wednesday and April 19 at the Barns at Wolf Trap, 1635 Trap Road, Vienna, Va. Tickets are $35. Call 410-481-6500 or 800-955-5566, or go to wolftrap.org.