Opposite problem than most — how do I get kids to talk, interact, and sing more?

In my first year of teaching HS in an urban setting. Most kids come from all over the city and they know very few people when arriving as freshmen. There is gang activity as well, but I haven't had to deal with much in my classes.

I teach a variety of music subjects and we also have the issue of arts classes being used as dump classes, and no study halls or free periods besides lunch.

While I'm working on building a program, I wish that I wouldn't have to wait till next year to have kids talk to each other, or to stop being so afraid to sing in choir class. I feel like I have a good relationships with students but there's always this sense of tension between my kids, that they are essentially just always hiding from each other.