THERE ARE MANY performers who just aren't cut out for life in a pop group. Some of them, unfortunately, find that out only after they've done time in a band; the luckier ones realize it right away and never even bother to merge their musical identities with those of others.

In either case, the decision to go it alone can make for some exciting and quite distinguished music. That's shown by the following recent "solo" pop record releases.

PETER GABRIEL (Atco SD 36-147). As lead singer and eminence grise for Genesis, Peter Gabriel made a virtue of unpredictability, fashioning a highly personal and instantly recognizable style out of the unlikeliest of materials. He has extended himself even further on his first solo album, bending the blues to his own purposes on "Waiting for the Big One," updating the barbershop quartet for a pleasantly psychotic number called "Excuse Me," and deploying the London Symphony Orchestra on the unsettling "Down the Dolce Vita." Though disappointing in some respects -- there's too much of producer Bob Ezrin and his cronies and not enough of English art-rocker Robert Fripp -- this album is a brilliant realization of Gabriel's bizarre outlook. It is perhaps most fascinating on the opening two numbers, "Moribund the Burgermeister" and "Solsbury Hill."

GARLAND JEFFREYS: Ghost Writer (A&M SP-4602). Perhaps even more than Lou Reed, Garland Jeffreys has come to be seen as the quintessential New York street kid. His music is tough and his attitude brash, but Ghost Writer, his first album in five years, is not without its romantic tinges. The rambling "Spanish Town" and the reggae fantasy "I May Not Be Your Kind" probably best typify this aspect of Jeffrey's personality, though the relatively straightforward "35 Millimeter Dreams" and "Why-O" also suggest that Jeffreys is a closet idealist. Known primarily as a singer-songwriter, Jeffreys proves he knows how to rock 'n' roll with the Rolling Stones-influenced "Wild in the Streets" and the defiant "Rough and Ready."

VALERIE CARTER: Just A Stone's Throw Away (Columbia PC 34155). Any singer who's comfortable with the styles of both Little Feat and Earth, wind and Fire obviously has something unique going for her. Valerie Carter, who has sung backup vocals with both groups, gets production and songwriting assistance here from Lowell George and Maurice White, but the main attraction is her eminently flexible voice. She moves from the countryish ballad "Face of Appalachia" to the easy-going funk of "So, So Happy" and "City Lights" with astonishing ease, stopping along the way to dabbie in straight pop ("Ooh Child") and jazz ("Back To Blue Some More"). A most impressive debut.

ROBIN WILLIAMSON: Journey's Edge (Flying Fish FF033). Williamson's first American album since the breakup of the Incredible String Band, with which he was associated for some ten years, contains a healthy dollop of Celtic and other traditional music forms of the British Isles. The "Merry Band" he's assembled includes a full-time harpist, a fiddler and a fellow who doubles on accordion and whistle, so he's well-equipped for that kind of sound -- as "Mythic Times" and "The Tune I Hear So Well" make clear. The quirky sense of humor that was the trademark of the ISB surfaces on "Rap City Rhapsody" and a revival of the improbable "Maharajah of Magador."

ROGER McGUINN: Thunderbyrd (Columbia PC 34656). It's ironic that the man who founded and led one of the most influential groups in the history of rock should choose to open his fourth solo album with arriviste Peter Frampton's "All Night Long." But the truth is that Roger McGuinn hasn't had a hit record since he disbanded The Byrds, and he'd obviously like one. So in addition to fine interpretations of a new Dylan tune, "Golden Loom," and George Jones's "Why Baby Why," McGuinn and his new band have turned to some younger names for help. If there's a hit single here, it's in a splendidly wistful version of Tom Petty's "American Girl."

BLONDIE CHAPLIN (Asylum 7E1095). Even though he co-wrote "Hold On Dear Brother" and sang lead vocal on the classic "Sail On Sailor," there are those who say that Blondie Chaplin never really fit in with The Beach Boys. They may be right: Chaplin, born and raised in Durban, South Africa, emerges on his first solo album as a spunky rock 'n' roller with a decided liking for the British way of doing things. There are strong echoes of The Beatles on "Woman Don't Cry," The Who on "Can You Hear Me" and The Rolling Stones on "Be My Love," and on "Riverboat Queen," Chaplin sounds remarkably like Bad Company's Paul Rogers.