During the day’s second rehearsal, however, she tempered her enthusiasm with tacit worry about her voice. She told her tour manager that Taja would soon be backstage, probably with a prednisone prescription. “Mom, I’m already here,” the 16-year-old screamed, 20 rows back in an otherwise empty arena. “I have your medicine! Do you want it?”

McLachlan couldn’t hear her. She nodded to her band and started a song called “Fallen,” humming to herself.

DURING SUMMER BREAK between sixth and seventh grades, McLachlan’s friends in Nova Scotia labeled her a lesbian. She had indeed kissed another girl, practicing for a boy. She instantly became a pariah, a middle-class kid from a conservative family surrounded by wealthy bullies.

“I became poison. Then they started calling me ‘Medusa,’ because I had long, curly hair,” she said. “There was physical abuse, too. I thought, ‘I am on my own.’”

There was little quarter at home. McLachlan was the youngest of three adopted children that she said her father never wanted. Since he tormented her older brothers, her mother — unhappy with marriage, depressed by circumstance — responded to her daughter with equal disdain, ensuring everyone was miserable. “I didn’t have a relationship with my father, because my mother wouldn’t allow it. If I showed him any attention, she wouldn’t speak to me for a week,” McLachlan said, lips pursed.

Music, however, became her refuge. She graduated from ukulele at 4 to classical guitar at 7 after the family moved to the provincial capital. She struggled in school, skipping class to hide in the empty gymnasium and play piano there. Though she despised the hard stares and high expectations of recitals, she begged to join a band. Her parents relented to a few hours of Sunday practice. The group’s first show, for several hundred dancing kids in a student union, was transformational.