For most of the 25 years since the be bop revolution, jazz singing seemed to have been left behind. While every other instrument was adjusting to one new breakthrough after another the voice was still back in the swing era of Billie Holidary and Al Hibbler.

Jazz singing faced a basic problem: it had moved away from composed songs to improvised music. Few singers were willing or able to forsake their training in the dramatic delivery of lyrics and use their voices as improvisatory instruments.

But within the past few years the talent has finally surfaced. The dominating figures are Flora Purim and Al Jarreau. Coming in their wake is a new generation of singers that includes Michael Franks, Angela Bofill, Jay Clayton, Norma Winstone, Gayle Moran, Patti Austin, Lani Holmes and others.

Excepts for Franks, these singers have had their best success using the voice as a wordless, improvising instrument. Most successful has been Purim, who has largely abondoned lyrics for short verses and chanted phrases. Her seemingly limitless soprano resonates like a Wayne Shorter soprano sax but cuts like a Woody Shaw trumpet.

Released from metrical lines of words, her voice (milti-tracked on albums) relentlessly attacks each song, breaking it open for higher harmonies and new bridges. The Brazilian born Purim adds colorful Latin touches to her improvistions. Perhaps her most ambitious album is last year's "That's What She Said" (Milestone -0981).

Jarreau still uses lots of lyrics, but is at his best when he leaves them behind. He seems to have a whole ensemble in his throat. When he scat sings syllables, his voice sounds like a plucked acoustic bass, the like a popping conga, then a punchy trumpet, then a soraing soprano sax, then a fuzzy electric guitar.

His most recent album, "All Fly Home" (Warner Brothers BSK 3229), suffers from mechanical arrangements and schmaltzy material. Far better is the two-record live album, "look to the Rainbow" (Warner Brothers BZ 3052), with its vocal fireworks interpretation of Paul Desmond's "Take Five."

Many of the new female jazz vocalists openly imitate Purim's breakthroughs. Angela Bofill's debut album, "Angie" (Arista GRP 5000), reveals Purim-like pyrotechnics, though much of the potential i smothered by Dave Grusin's heavy-handed production.

The 24-year-old Bofill's best moments come on her own Latin-tinged "Under the Moon and Over the Sky". As she chants the title line in here unfaltering voice, she leaps halfway through "sky" into an upper register release. In a long, improvised section, she lets go of startingly pure high notes in staccato bursts and make stratospheric singing sound easy.

but on the very next song, arranger/producer Grusin ties her down in a syrupy pop ballad, "This Time I'll Be Sweeter." Bofill hits every note with laser precision, but the arrangement bogs down in doodling electric piano and anonymous string and choral sections.

The whole album reflects this battle between Bofill's soprano acrobatics and Grusin's clutter. Her best opening comes on the four song she wrote herself.

Jay Clayton shows much more than potential on byron Morris & Unity's "vibrations, Themes & Serenades" (EPI-03). This is a local group recording on their own label in Wheaton, but Clayton in a major talent. She uses her voice as one of the seven instruments in Morris' ensemble, and her solos stand out on every cut.

"ERAA" builds a likeable rushing momentum as the saxophone and trumpet take their solos. But when Clayton's rordless solo comes, she mixes darting squiggles and resonating arcs with the leapong imagination that changes a jazz solo from craft to revelagtion.

Michael Franks goes in the opposite direction of these other singers. He reemphasizes the role of lyrics and gets away with it because he's one of the most gifted lyricists to ever work in jazz. He latest album. "Tiger in the Rain" (Warner Brothers BSK 3294), is filled with images of a hostile, dangerous outer world and secret, romantic sanctuaries.

The images are created by sparse phrases with sharp details that evoke more than they state. The outer world is: "Zombie trains/Midnight planes/Stews are too acidic/Not to mention/Kansas City critics." One of the inviting sanctuaries is: "Cloud days we stay inside together/The weather's wet/The tea is from Tibet/I play the scales/And you protect the Whales."

The music is soft, romantic jazz. Franks doesn't dominate the songs like most jazz singers, but creates a minimal outline for the superb musicians to fill in. Franks will sing a calm, breathy line that follows the melody and no more. Then the line's lyrics will be expanded with a short echoing line by one or more musicians.

On "Tiger in the Rain", Ron Carter's sliding bass notes evoke the scared growl of Franks' intimidated tiger, while Michael Mainieri's vibe notes fall like a gentle rain. On "When It's Over," Joe Caro's human voice-like guitar phrases carry the tension of breaking up that Franks' singing lacks. In the same song, Purim's voice swirls up around Franks' and gives another extension to his lyrics.

Few singers have Purim's gift for using the voice as an inventive jazz instrument. Even fewer have Franks' gift for fitting fine lyrics into jazz settings. But jazz singers with these talents ahve emerged and jazz vocals are finally catching up.