Billed as a mixtape rather than a proper album, The Greatest Gift finds Sufjan Stevens taking a second look at the music and themes of his 2015 album Carrie & Lowell, a beautiful but sometimes harrowing and deeply personal examination of his relationship with his parents and the death of his mother.

For The Greatest Gift, Stevens has given us four previously unreleased tracks that lyrically and stylistically are of a piece with the original album ("Wallowa Lake Monster," "City of Roses," "The Hidden River of My Life," and "The Greatest Gift"), an iPhone-recorded demo ("John My Beloved"), remixes of several other tracks, including two versions of "Drawn to the Blood," and "Exploding Whale," a non-LP single side.

While the spare, stark approach of Carrie & Lowell would hardly seem to be traditional remix material, the reworked versions that appear here are executed with taste and skill.

The ghostly distorted vocals hovering in the background on "Fourth of July [900X Remix]" are inspired, Helado Negro's remix of "All of Me Wants All of You" gives the tune a stronger pulse but doesn't compromise its emotional force, and Stevens' mix of "Drawn to the Blood" that reduces the backing to a fingerpicked mandolin cuts straight to the heart.

Of the new tunes, the childhood memories of "Wallowa Lake Monster" and the spiritual contemplation of the title song connect beautifully, and if they aren't quite up to the standards of the original album, they're welcome additions to this appendix.

The Greatest Gift works best as a companion piece to Carrie & Lowell, a variation that offers a different spin on its themes, but it's also a powerful and absorbing work in its own right, and fans of Stevens' work will appreciate it.