Mariah Carey's new album, "Rainbow" (Columbia), has already yielded its first No. 1 single, "Heartbreaker." That song is Carey's 14th No. 1--leaving her behind only the Beatles and Elvis Presley. But "Heartbreaker" is one of Carey's slightest achievements, a frothy romantic regret that samples Stacy Lattisaw's "Attack of the Name Game" and uses a very polite guest rap from Jay-Z. A far more interesting, and far livelier, remix featuring the ubiquitous Missy "Misdemeanor" Elliott and Da Brat, as well as a replacement sample from Snoop Dogg, also appears on the album.

"Rainbow" navigates the two Mariahs--the pop singer who can belt out treacly Diane Warren uber-ballads and sophisticated R&B plaints by Jimmy Jam and Terry Lewis, and the street-smart, hip-hop-partial diva who hangs with Jermaine Dupri and Master P. Carey's superstar status is confirmed with the inclusion of two Warren tracks: "Can't Take That Away (Mariah's Theme)," a hackneyed self-empowerment anthem for an upcoming movie, and the self-doubting "After Tonight," which gets a boost from producer David Foster. The lush romanticism of the latter song, underscored by Dean Parks's supple Spanish guitar, lets Carey effectively work the lower range of her voice, as does "Crybaby," a New Jill Swing-flavored track with Snoop Dogg guesting live.

Overall, the new album is a major disappointment. Carey's stratospheric vocal excursions, absent in her recent work, reappear in "Bliss," one of four Jam/Lewis tracks. Alas, Carey skies out like Minnie Riperton with no particular benefit to the song. The other Jam/Lewis efforts include the melancholy but ponderous "Petals" and the inspirational "Thank God I Found You," in which Joe and 98 Degrees vainly sub for Carey's former collaborators Boyz II Men.

Much as she may love hip-hop, Carey is not really well showcased in that context. "Did I Do That?," co-produced with Master P and Craig B. and featuring brief raps from P and Mystikal, is all over the place with layered vocals, pizzicato strings, bubbly bass and drums--but no melody. The singer simply disappears in the sleek, skittish rhythms produced by Dupri on "How Much" and She'kspere on "X-Girlfriend," both of which make Carey sound like a dozen less gifted mini-divas working the same tired territory. She should know better.

(To hear a free Sound Bite from this album, call Post-Haste at 202-334-9000 and press 8175.)

CAPTION: With more No. 1 hits than anyone except the Beatles and Elvis, Mariah Carey has felt free to experiment with new forms, but as her latest album shows, not always with complete success.

CAPTION: Carey's latest album, a mixture of romantic ballads and hip-hop, doesn't do justice to either genre.