They sing sweetly about men going off to war and their lovers waiting behind. If you think that’s an old-fashioned notion, it’s only because The Tetseo Sisters from Nagaland, who perform in the city today, are taking ancient Naga folk songs out of forgotten memories and redoing them in a special way. The Tetseo sisters — Mercy (32), Azi (31), Kuku (25) and Lulu (23) — sing in Chokri, a dialect from the Phek region in Nagaland. “We realised no one was doing this. As sisters, we had been singing together ever since we were children — at church or in school.