Sinead O'Connor's latest revelation? Nothing compares 2 Jah!

Emerging from a two-year retirement, the mercurial Irish singer has transformed herself into a full-fledged reggae artist -- to the point that she's now eschewing material from her own catalogue. (Maybe it's not a complete transformation, though: The doe-eyed waif, who played Tuesday at the 9:30 club, still sports a shaved head. Which made her simmering performance of Lee "Scratch" Perry's "Curly Locks" that much more intriguing.)

During a set that ran for almost two hours, the preternaturally talented vocalist ignored her best-known pop songs ("Mandinka," "The Emperor's New Clothes," the Prince-authored smash "Nothing Compares 2 U") and instead explored the roots-reggae canon, including all 12 songs from her new album of reggae covers, "Throw Down Your Arms."

Fronting a band anchored by the great reggae production duo/rhythm section of Sly Dunbar and Robbie Shakespeare, O'Connor sang well-established protest songs, including Burning Spear's "Marcus Garvey," Bob Marley's "War" and an impassioned rendition of Peter Tosh's "Downpressor Man" that was dedicated to President Bush.

O'Connor also sang Jah's praises. Earnestly and often.

"He will take us by our hand / And lead us to the wonderland," she declared during a rich, harmonic cover of the Abyssinians' "Y Mas Gan."

Forever restless about religion, O'Connor -- who defiantly tore up a photo of Pope John Paul II on "Saturday Night Live" 13 years ago -- seems to have found considerable comfort in Rastafarianism. A champion of spirituality over clergy (and never mind that she herself has been ordained as a priest by a fringe Catholic group), she writes in the liner notes for "Throw Down Your Arms" that Marley, Spear, et al. "were part of a battle fought for self-esteem and for the freeing of God from religion."

The legends' music, O'Connor adds, "raised God from the dead in the soul of a little Irish Catholic woman."

And so Tuesday, there was O'Connor -- who used to seethe onstage -- grinning and appearing completely at peace, as she delivered an enthralling performance of Tosh's "Creation," sweetly singing: "Jah is my kingdom / Jah is my light and my salvation / So whom shall I fear?"

An audience member shouted "Nobody!" and O'Connor's smile broadened as she whispered into the microphone: "That's riiiiiight."

Nothing to fear, including Burning Spear himself: While Willie Nelson failed miserably in his attempt at releasing a credible reggae record this year, O'Connor's effort -- recorded with Sly and Robbie at Tuff Gong Studio in Kingston, Jamaica -- is a resounding success.

In large part, that's because O'Connor was smart and respectful enough not to overhaul the originals. Instead, she paid tribute through faithful remakes, with just a few key changes to better suit her voice.

So, on the album and onstage, "Downpressor Man" sounds basically the same as it ever was -- although, given the distinct nature of O'Connor's keening vocals along with her brogue (not to mention the jigs O'Connor does), it's impossible for her to avoid putting her own stamp on the songs.

Let's call them reggaelic.

(One bizarre side effect: We couldn't help but giggle when O'Connor sang, on "War," in a lilting voice, that "we Africans will fight.")

Of course, O'Connor is no Johnny Clarke-come-lately, even if she did include Clarke's "Move Out of Babylon" in her set.

She's long dabbled in reggae, writing Rasta-inspired originals like 1994's "Fire on Babylon," and her anti-Vatican statement on "Saturday Night Live" came at the end of a performance of "War."

But she's jumped in with both feet now, performing with an expert eight-piece band of reggae veterans led by Sly and Robbie (on drums and bass), who frequently led the group into instrumental dub breakdowns. Also in the band was the trombonist Nambo Robinson, who doubled as O'Connor's hype man: Robinson, who has played behind Spear, among others, approvingly introduced the star of the show as "sister Sinead," who had come "all the way from that irie-land they call Ireland." (For those not up on their Jamaican patois, "irie" more or less translates to "a state of bliss.")

In addition to the band, O'Connor was supported by two singers who helped rescue the lead vocalist at several points when her voice -- strained and raspy from the first few dates of a North American tour -- had trouble carrying the melodies by itself.

The trio sounded best when interlocked on three-part harmonies, as on "Y Mas Gan." Sometimes, though, as in the opening performance of Spear's "Jah Nuh Dead," O'Connor had to go it alone vocally, and the songs suffered.

Then again, it could have been her insistence on frequently holding the microphone away from her mouth as she wailed -- sometimes at her hip, sometimes a full foot and a half in front of her face.

Still, she's a remarkable live performer, and even on a night that might not have been her best, O'Connor was riveting and righteous.

Nothing compares, indeed.

Sinead O'Connor brought a full complement of earnest reggae covers to the 9:30 club Tuesday.