Happy Medium is an NYC-based collective of old college friends, their much-more-talented spouses, and other accountants and lawyers who play cover songs for millennials, mostly. Think about what you used to listen to and love when you were like, 17. Ohhh yeah. Breathe it in. That’s the good stuff. Nostalgia. It’s delicate, but potent. Teddy told us that in Greek, nostalgia literally means “the pain from an old wo...