There are voices, and then, there are voices.

Two of the absolutely most spine-tingling, toe-curling, soul-caressing voices I know belong to Irma Thomas, the long-reigning Soul Queen of New Orleans, and Tracy Nelson, former Earth Mother of the psychedelic era. Both are present on this recording, and put on as fine a display of vocal pyrotechnics as either has produced.

Ever since thundering onto the scene with her band, Mother Earth, and their full-throttle debut, Living with the Animals (featuring “Down So Low,” constructed around a set of gospel chords), Nelson has consistently covered Thomas’ hits (“Cry On,” “Ruler of My Heart,” “Done Got Over,” ” I Wish Someone Would Care,” and even “Time Is On My Side,” the title of a Nelson album dedicated to Thomas) and adapted a few of her vocal techniques. Nelson opens the door with a pair of moving ballads, “In Tears” and “Heart to Heart,” that explore the ocean’s floor of her blue-bottomed range, and then lets the depths come screaming to the surface on “Please No More,” providing her own surging, keyboard accompaniment.

All three contributors sing unison (in lovely, earthy, uncontrived harmony)on a pair of lively numbers: the galloping “I Want to Do Everything for You” and “Shouldn’t I Love Him,” a piece of Memphis funk overlaid with nostalgic ’50s girl-group embellishments.

But the most riveting drama here belongs to Thomas, who seems to have discovered firm ground on which she can make a mid-life stand. “People Will Be People” is so natural for her it sounds already classic (with spoken asides like, ” … and dogs will be dogs ….”). “Woman on the Move” gives her a long-sought-after, defiantly joyful anthem (“I’m a woman … on the move … with a mission ….”). “Yield Not to Temptation,” with its driving, Hammond B3 from guest organist Davell Crawford, provides the perfect alchemy: a righteous take on earthly love nestled comfortably in gospel language and fervor. And on the last cut, “You Don’t Know Nothing About Love,” both Thomas and Nelson are set loose in a soul-searing lovefest of a duet, playing off each other, soaring, swooping, leaning back on their heels, coming in with a shout, for a rafter-shaking performance.

This is the most powerful singing anyone’s done in a long time.