Named for Loch Altan, a lake in the group’s native County Donegal, Altan is a folk-rock band only in the sense that it’s aware of rock: Singer Mairéad Ní Mhaonaigh calls one of the sextet’s models, fiddler John Doherty, “the Jimi Hendrix of Irish music.” The quintet’s latest album, Runaway Sunday, may be on Virgin and boast an arty cover, but it balances the traditional elements of Irish music: jigs and ballads, jubilation and despair, immediacy and nostalgia. Mhaonaigh’s voice embodies the music’s downbeat side, and the band plays with greater abandon than ever. See Altan at 8 p.m. tonight and tomorrow at the Barns of Wolf Trap, 1624 Trap Rd., Vienna. $16. (703) 938-2404. (Mark Jenkins)