Historically, Sting has done pretty well as the singer for a three-piece band. Sting, who just joined Billy Joel onstage in Tampa, can certainly afford to hire more musicians if he wants, but for his next American tour, he’ll go back to his roots, fronting a newly formed power trio. On the Sting 3.0 tour, Sting and his bandmates will play relatively small venues, and maybe they’ll flex some of the anxious, urgent intensity that Sting had with the Police.