With all rock performers, but especially with so-called "singer/ songwriters," the element of persona is crucial to an understanding of the artist's work.

J.D. Souther's third solo album, "You're Only Lonely" (Columbia JC 36093), presents a portrait of a fragile, withdrawn, shattered man. (Appearances deceive: Although Souther is a founding member of the Los Angeles country-rock coterie, in the record's cover photographs he resembles cartoonish Garry Trudeau's newspaper reporter, Rick Redfern.)

Souther has achieved recognition primarily through other musicians' interpreations of his songs. Yet he is an important composer, constructing careful harmonies and precise vocal arrangements. The album is impeccably engineered and produced (Souther served as producer) and features Los Angeles session regulars such as guitartists Danny Korchmar and Waddy Wachtel, bassist Kenny Edwards, and drummer Rick Marotta -- all accomplished professionals, and perhaps best known as Linda Ronstadt's band.

"You're Only Lonely" is a persistent exploration of Souther's thorough absorption in his own sorrow, almost monochromatic in its composer's obsession. The title track and "If You Don't Want My Love" mask Souther's glumness with lilting, delicately soothing melodies.

Two compostions have been recorded strikingly by other singers. Nicolette Larson's husky, throaty version of "Last in Love" appears on her 1978 debut album, while Linda Ronstadt's amazings powerful rendition of "White Rhythm and Blues" is included on her "Living in the U.s.a." Souther's more melodical delivery of both selections is, by contrast, simple and plaintive.

"The Moon Just Turned Blue" is a funny throwaway, a parody of country-and-western misery. The belligerent "Till the Bars Burn Down" begins promisingly, but the forthright guitar line and drumwork don't save if from disintegration. "Fifteen Bucks" continues the brooding, surly theme of what critic Janet Maslin calls the Hollywood barfly-outlaw" and carries it to extremes; the song is lame and silly.

"Songs of Love" (which bears a vague similarity to the Eagles' "Take It to the Limit") is meticulous, a subdued meditation on the singer's failures. "Trouble in Paradise" is the most rousing cut on the album; it's an energetic remake of a song recorded by the ill-fated Souther Hillman Furary Band in the mid- 1970s. Souther's reworking is rich and full, supplemented by David Sanborn's currently fashionable, expertly played saxaphone. Souther is immaculate -- even when he rocks; he never gets his hands dirty.

"You're Only Lonely" is a modest album, but it isn't a bad one. Despite Souther's tendency to overindulge in self-pity, it's a preasure to listen to a male songwriter who's not afraid to acknowledge and appraise honestly his dissastisfaction, fears and shortcomings.

Walter Egan, too, has recorded a third solo effort, "Hi Fi" (Columbia JC 35796). Egan is a former Washingtonionan who now lives in Los Angeles, and "Hi Fi" would like to show us how much fun it is to write songs and party in the (high-tech rather than laid-back) ambience of the California music industry. What the album actually reveals, however, is merely the extent to which rock songwriting is a routine and mechanical chore. It doesn't tell us much more than that because Egas hasn't yet drawn out any one aspect of his songwriting personality and expanded it satisfactorily.

Egan is perfectly competent composer of short pop songs intended for Top 40 radio airplay; he writes imaginative instrumental parts and his guitar solos are concise if obligatory. He has clearly been influenced by the intricate multiple harmonies and shiny disposable esthetic of the Beach Boys -- indeed, the album is dedicated to Brian Wilson. The unrelenting beat and male/female counterpoint (vocalist Annie McLoone contributes sparkling harmonies and is the most impressive member of Egan's back-up "Professional Band") suggest a low-budget Fleetwood Mac. Egan seems to want to play Lindsey Buckingham to McLoon's Stevie Nicks (and, indeed, Buckingham and Nicks were involved in his first two LPs). But he's only fitfully successful in his Fleetwood Mac imitation because "Hi Fi" lacks that group's interplay among several members who each possess a distinctive trait of writing or performances. It's this counterbalance of styles that supplies a band such as Fleetwood Mac with dramatic tension.

Walter Egan earnestly writes troubled, catchy laments: "I Can't Wait," "That's That," "Hi Fi Love," "Bad News Travels Fast." But his lyrics are too often overwrought, his musical structures too tedious to support them. More than anything else, "Hi Fi" indicates that Walter Egan, promising musician that he is, should find himself a full-flidged band.