Christina Aguilera sings “Mother” with a cool vibe on Instant Karma.

AP / MICHEL SPINGLER MICHEL SPINGLER

Green Day covering “Working Class Hero”? Majestic. Avril Lavigne warbling “Imagine”? Majestically tone deaf.

Released last week, Instant Karma: The Amnesty International Campaign to Save Darfur is a double-disc charity compilation of pop hotshots paying tribute to John Lennon. The entire 23-track CD will cost you about $15. (There are also a few tracks available as digital downloads only.) But this is the iPod age, and drastically uneven collections such as this were made for picking and choosing.

However you spend your money, it’s going to Amnesty International and its fight for human rights. (Lennon widow Yoko Ono donated publishing royalties to the cause.)

Because we care, here’s a download-friendly guide to the best and worst of Instant Karma:

Instant goodness

•The Flaming Lips, “(Just Like) Starting Over.” Singer Wayne Coyne’s spacey sweetness soars over laser-gun synth. Go hug somebody. Now.

•Regina Spektor, “Real Love.” The Moscow-born singer will flat-out floor you with this vaguely baroque, chilly take on an overlooked gem.

•U2, “Instant Karma.” Too easy, too obvious for the Dublin Four? Maybe. But Bono was born to sing “Well we all shine on!”

•Christina Aguilera, “Mother.” There’s a cool, stuck-in-the-’70s vibe here, as a refreshingly mellow Aguilera strives for emotion more than emoting.

•Corinne Bailey Rae, “I’m Losing You.” British neo-soul chanteuse nails the smoldering desperation in this breakup great.

•Green Day, “Working Class Hero.” Billie Joe Armstrong’s everyman rallying cry swells to an epic, rumbling finish. Using Lennon’s voice in the finale is yet another stroke of genius from a band that can do no wrong.

Cold turkeys

•Aerosmith featuring Sierra Leone’s Refugee All-Stars, “Give Peace a Chance.” This makes me want to declare war on Steven Tyler, who sounds as if he’s being attacked by wolverines.

•Snow Patrol, “Isolation.” When comparing snoozy, self-important Brit-pop bands, Snow Patrol makes Coldplay sound like the zany life of the party. That ain’t easy, kids.

•Lenny Kravitz, “Cold Turkey.” This is right in Lenny’s wheelhouse. That said, Lenny’s wheelhouse is overflowing with cheap, slimy knockoffs of his heroes.

•Jakob Dylan featuring Dhani Harrison, “Gimme Some Truth.” Gimme some NoDoz is more like it. Bob’s kid and George’s kid should have rocked this one.

•Avril Lavigne, “Imagine.” We could be really mean here. But remember: John Lennon preferred women who couldn’t sing a lick.