Chan Marshall, a.k.a. Cat Power, is indie rock’s homespun gadfly — a mopey bundle of disconsolate lullabies whose uneven live performances threaten to eclipse her quiet genius. Cat Power’s seventh album, The Greatest, offers something beyond the cavernous longing her fans have come to expect. This time Marshall teams up with classic Memphis soul legends guitarist Mabon Hodges, who strummed for Al Green, and drummer Steve Potts, who jammed with Booker T & the MGs. It’s unexpected company for a maladjusted chanteuse, and the band’s slinky Seventies beat at times threatens to overwhelm Marshall’s warm, throaty warble. Smoky ballads such as the title track — a bittersweet wee-hours-of-the-night rumination — catch Marshall at her most sincere and suggestive. However, her barely-there lilt is drowned out by a salvo of Memphis horns and string arrangements throughout most of the album. Marshall is not a diva — her songs are private compositions that sound like they’ve been painfully wrenched from her — and placing her against a backdrop of dulcet doo-wop harmonies doesn’t seem quite fitting. Fans of Seventies Stax Soul will welcome Potts and Hodges’s return, yet followers of Marshall will mourn that singers’ sudden departure.