Sometimes collaborations between classical groups and musicians who play other genres of music founder for lack of a shared vision or commitment. But Pink Martini, the self-described “house band of the United Nations,” is a case where the opposite is true: They're so much fun with an orchestra behind them, that you want them to do it more. That's why they are back for their third tour of duty with the San Francisco Symphony. The eclectic mix of world music and pop is hip on its own, but their arrangements, already for an expanded band, make them a great fit for an orchestra. If you're looking to start the pops season out right, this is a danceable, singable treat that sells out every year.