Activist street bands will fill the streets of Somerville and Cambridge this weekend for the 2015 edition of HONK! Fest. The festival’s hosts describe it as a street music revolution in which bands present a diverse fusion of folkloric and modern sounds in the spirit of Mardi Gras. The festival is for free and will run throughout the weekend. For more information on the bands and the festival, please visit the official HONK! fest homepage or their Facebook page.