The members of Chesterfield hip-hop trio CommonYouth — Brian DeCosta, Matt Moseley and Tyler Prillaman — have been together for only half a year, but already they’ve released a video and been in several hip-hop showcases. They recently issued “SideTracked,” a nine-track mix tape. The trio takes pride in its suburban upbringing, and maintains that being true to themselves is essential to their music. “You don’t have to be a gangbanger and selling drugs to be doing hip-hop,” DeCosta says. To record “Mind of CommonYouth,” the group cleaned out DeCosta’s closet and turned it into a studio. “It was actually the third song we ever made,” he says. Since “SideTracked” dropped, CommonYouth has been working on another mix tape, which it plans to release this summer. “The new stuff we have just blows [“SideTracked”] out of the water,” Moseley says.