For her first album since her breakthrough hit “Chandelier,” Sia is facing off on the charts against superstars Adele and Rihanna. And they are likely familiar with some of the songs — they were written for them.

“This Is Acting,” the seventh album by the Australian singer known both for her distinctively soaring voice and her face-covering black-and-white wig, consists of tunes that she wrote, offered to other artists and, after deals fell through, salvaged.

For Sia, the album is a multidimensional paradox. She is interpreting her own songs, ones that are often highly personal. But they were intended to come from the hearts of others. The album’s first single, “Alive,” was meant for Adele as part of her blockbuster album “25.” “Alive” matches the mood of “25,” as Sia — playing the role of Adele — reminisces of her childhood and her survival into adulthood to a tune that opens with richly dark piano chords before a rapid climax. “I’m still breathing / I’m alive,” sings Sia in one of her strongest performances, her voice gliding from soulful to roaring with a touch of rasp.

Sia, speaking to Apple Music’s Beats 1 radio, said she was surprised that Adele did not want “Alive.” “I thought this one was such a smash but she just wasn’t feeling it,” Sia told the station, whose host Zane Lowe described the album’s concept as playing “fantasy football with the world’s pop stars.” Sia similarly appears to channel Beyonce on the more inspirational “Footprints,” a string-backed, mid-tempo pop song that uses subtle spiritual imagery to describe salvation either by a partner or God.