When do you become an adult? Legally it's 18, of course, but it used to be 21, so that takes some of the fun out of it. If it's already changed once, then what's to stop it changing again in the future? I remember turning 18 and not feeling any different at all. It's hard not to see how arbitrary it is. Instead, we turn to milestones in our lives. The first time you vote, or have sex, or get drunk, or get drunk and then . . .

Laura Veirs has butterfly wings and a guitar in her hands. Half-way through a song, she's interrupted by an excited child, killing the sound with a careless knock of the amp. "Watch out," she warns gently as a technician fixes the situation, "our equipment is made of lava." At her gig in the crowded basement of the Museum of Childhood, parents politely jostle to catch a glimpse of her, forgetting themselves and singing . . .