A performer dubbed "the Irish Michael Bublé" — you're already intrigued, aren't you? — Nathan Carter is only 26, but in his native country he is a very big deal. He's already produced three albums and two singles that have topped Irish charts. But while he is a star in Ireland, he's an unknown quantity in the United States ... perhaps not for long, though. Carter is on his debut North American tour, and his upcoming concert at Hochstein's Performance Hall this Friday will feature Chloë Agnew, an original member of Celtic Woman, in "a program packed with old country favorites, Irish folk songs, and adult contemporary classics" as well as turns on the guitar, banjo, and accordion. Even Michael Bublé can't do all that.