>> mitchell: finally this evening, they have an army of fans and a chart-topping holiday hit. what's unusual is that they're a choir. charlie d'agata in london has the story behind the song. ♪ ♪ eporter: ir: in a windswept corner of england, a group of military wives struggling with the stress of having husbands on the front lines have found a way toway to deal with it; they sing. ephenson'stephenson's husband is an army engineer with the 24th regimedo regiment. >> when he first left for afghanistan, i think that was the worst because that could literally be the last time i see