If you entered the back of the Giant Center Sunday night, then listened and squinted toward the stage, you might have thought you'd been transported back to the 1960s. There's diminutive music icon Paul Simon, singing in harmony with a tall guy. But that taller guy is playing the bass. And his name is Sting. The two musical icons performed mostly separately, and momentarily together, during the Hershey stop on their minimalistically named the "On Stage Together" tour before a large and appreciative crowd. In that crowd, hands swayed, fannies shook and couples snuggled, ensconced in nostalgia that spanned two famous singer-songwriters' oeuvres from the '70s through the early years of the new millennium...

It's one thing for two longtime stars to share a double bill that pools their audiences and lets them play larger places. It's another to do what Paul Simon and Sting are doing on their arena tour together: actually to team up for about one-third of the concert, sharing songs and mingling the 14 backup musicians from their bands, displaying mutual respect without undue deference. (The tour has two T-shirts: one that reads "Paul Simon & Sting on Stage Together," the other vice versa.) On Tuesday night at Madison Square Garden, where the tour returns on Thursday, the pairing loosened up two ambitious songwriters whose perfectionism has earned them long careers, shaking up their neat routines. As they rotated on and offstage, singing together between minisets with their own bands, they revealed both their kinship and their differences. And now and then, they played comedy team...