Irish music group Altan has been keeping the traditional flame alight for nearly three decades. The band was formed in the late '80s, in County Donegal, by fiddler and vocalist Mairéad Ní Mhaonaigh (one of the foremost Gaelic language singers). Last year, Altan released Gleann Nimhe — The Poison Glen, their 11th studio album (and their first of original material in seven years). An Altan concert is a powerhouse performance incorporating guitar, bouzouki and accordion. The Irish band plays Diana Wortham Theatre on Thursday, March 21, 8 p.m. $30/$25/$15. http://www.dwtheatre.com.