Chris Willman Senior Music Writer and Chief Music Critic Attentive music fans have had some time now to become familiar with who and what the singer Laufey is: a young Icelandic-Asian-American woman whose traditional balladry often recalls the pre-rock era. Still, for a few of us, it might have come as a very slight surprise to see her step onto the outdoor stage of the Ford in Hollywood over the weekend and be reminded that she is 24 and not 124.