Talk about an endorsement: Danny Gallagher has performed with the Dropkick Murphys as a guest vocalist, in addition to national recording artists like Susan Tedeshi. More recently, he was invited to sing the national anthem at Fenway – for the second time. But don’t wait until July to catch his acoustic act. Following the the Red Sox game on May 7, Gallagher plays the Bleacher Bar. It’s a sure winner.