Boston Emissions presents 2016 Rock & Roll Rumble Semifinals Night #1 with Worshipper, Abbie Barret, usLights, Eric Salt & The Electric City on Friday, April 15, and Night #2 with Weakened Friends, Salem Wolves, Analog Heart, The Devil’s Twins on Saturday, April 16 at ONCE Lounge and Ballroom, 156 Highland Avenue, Somerville. Doors: 8:00 p.m., show: 9:00 p.m. (ends at 1:00 a.m.) each night. $13 in advance, $18 day of show. Online ticket sales: http://www.ticketfly.com/event/1091467. In association with Cuisine en Locale. Phone 617-285-0167 for more info.