It took rock 'n' roll almost three decades to produce its first No. 1 record by an all-female, self-contained band. Understandably, therefore, most of the attention lavished on the group last year centered on the novelty of its gender breakthrough. It took two convincing tours last winter to establish that the Go-Go's were no fluke. Now the group's follow-up album, "Vacation" (IRS SP70031), should train everyone's attention back to the music, where it belongs. The band appears at the Merriweather Post Pavilion tomorrow night.

The Go-Go's' platinum debut album, "Beauty and the Beat," recaptured the ebullient spirit of the early '60s "girl groups" over a thumping dance beat. Around the edges of this slumber party celebration, however, the attentive listener could discover dark traces of doubt and irony. "This Town" exposed the disillusionment behind L.A.'s glitter; "You Can't Walk in Your Sleep (If You Can't Sleep)" presented compulsive romance as unnerving insomnia.

The follow-up album takes a big risk by abandoning sock-hop innocence to bring the doubt and irony out front. "Vacation," already a hit single, is not a carefree ditty about getting away from it all. It's a revealing song about the inevitably futile wish to get away from it all. Belinda Carlisle's vocal mixes yearning with melancholy regret, while Gina Schock's sharp drumming and Charlotte Cassie's dark guitar chords drive home both the wish and the frustration.

"He's So Strange" is an even darker song that describes how women are victimized by romance, with Cassie's stabbing lead guitar bringing out the hints of violence in rhythm guitarist Jane Weidlin's lyrics. Carlisle--who belted out everything with a sunny party spirit last year--shows her new gift for understatement, murmuring the key lines ominously.

In another song Carlisle whispers wonderingly, "Don't know where I stand?" She reflects that in every relationship, one person gives more love than the other; then with the shock of realization, she shouts out the title line: "I Think It's Me!" Cassie's jangling, repeating guitar figure lends a certain faithfulness to the lyrics; she has improved dramatically since the last album, inventing catchy chord riffs and playing them with precision, like a female Keith Richards. Her descending guitar phrase captures the feeling of a relationship falling apart on bassist Kathy Valentine's "We Don't Get Along."

Every group member has improved noticeably since the first album. Weidlin has emerged as the band's best lyricist; her "Girl of 100 Lists" captures the obsession with detail that the confused hope will bring order to their lives. Schock's jungle-rumble drumming saves an otherwise slight song, "Get Up and Go." "It's Everything but Partytime" suggests the band's new sense of irony, and Carlisle's deeper, thicker voice is able to encompass these conflicting moods. Valentine unleashes a savage bass line on the surf rave-up "Beatnik Beach," which brings together Allen Ginsberg and Annette Funicello and proves the band hasn't lost its sense of humor.

The album's biggest disappointment is that the melodies are not as catchy as on the group's first record. Also, the cover version of the Capitols' "Cool Jerk" is not nearly as infectious as the live version they've done. Moreover, most of the best songs on "Vacation" are all on side one. Nonetheless, the Go-Go's have proved they're willing to take this and grow. They've grown a lot already and have the potential to become one of the decade's most important bands.

Now that the Go-Go's have opened the commercial gates, we should expect a steady flow of all-female bands. One of the first bands through those gates is the Catholic Girls, which had been laboring in New Jersey clubs before the Go-Go's broke. On the cover of its debut album, "Catholic Girls" (MCA 5350), the quartet wears the Catholic school uniforms (jumpers, saddle shoes and knee socks) that are its on-stage gimmick. Inside, the music reminds one of the yearning "girl group" vocals and New Wave big beat of the Go-Go's. Yet the Catholic Girls avoid becoming Go-Go's copycats, thanks to the strong songwriting of lead singer Gail Peterson, who penned all 10 tracks herself.

Peterson writes catchy pop hooks that build into grand crescendos, much like the old Phil Spector songs. Like the Go-Go's, she streamlines the Spector sound by stripping off the sweeteners, beefing up the rhythm section and bringing the guitars up to the vocal level. On "Boys Can Cry," Peterson reflects, "Boys, they're always trying to hold back the tears," over Joanne Hollins' throbbing bass line. More instruments and voices join to push the song to a big chorus where Peterson's grandly melodic threat, "Boys can cry, so why don't you stop making me," is countered by Roxy Andersen's falling high harmonies. "I Called You Up" is structured the same way, ending with an even better melody and this romantic confession: "Was too proud to tell you, Why can't you ead my mind?"

Peterson's biggest failing is her tendency to melodramatic singing. Too many lines are given an emotional quiver that's transparently contrived, which sabotages some very good lyrics. Catholic imagery pops up throughout the record. If Peterson can learn vocal understatement, her wit and melodic gift could make the Catholic Girls the second big all-female band.