Celebrating the Boston area’s abundance of Irish, Scottish, Cape Breton and other Celtic-related music and dance traditions, BCMFest (Boston’s Celtic Music Fest) begins its second decade on January 10 and 11, 2014. A program of Passim, the Eleventh Annual BCMFest will bring together dozens of the best local musicians, singers and dancers to three locations for dozens of performances as well as participatory music and dance events right in the heart of Harvard Square.