THOUGH RONNIE GILBERT is best known as the female voice in the Weavers' folk harmonies, she is most comfortable and effective with cabaret material. Her precise diction and phrasing are better suited to the formal demands of theatrical music than to the improvised feel of folk, country or blues.

She wisely emphasizes these strengths on her first solo album in more than 20 years, "The Spirit Is Free." Even Hank Williams' "I'm So Lonesome I Could Cry" is rearranged from a slurred confession into a piano-and- violin art song, with Gilbert's relaxed technique isolating the song's melodic beauty.

Gilbert's fervent admirer, Holly Near, contributed four compositions plus her production team to this album. Gilbert still has much to teach Near about the use of understatement and irony to set up punchlines. On wo Tom Paxton songs, Gilbert holds something back on the descriptions of stripmining and apartheid so she can wring out the conclusions all the more effectively.

Often the only instruments are Gilbert's sturdy voice and John Bucchino's cabaret piano; such restrained arrangements give simple songs like Connie Kaldor's "Wood River" and Judy Small's "Mothers, Daughters, Wives" the unburdened clarity they need.

Gilbert can also be heard on "HARP," which could be described as an '80s updating of the Weavers. HARP is an acronym for Holly Near, Arlo Guthrie, Ronnie Gilbert and Pete Seeger: two originals, one son of an Almanac Singer and one spiritual descendant. They share common concerns, common commitment and a humanist spirit epitomized by a line from one of their songs: "Struggle is long, but hope is longer."

Recorded live, "HARP" features several solo turns by each individual and supple ensemble work on several numbers. Best cuts are Gilbert's impassioned reading of Howard Bursen's "Small Business Blues"; Seeger's poignantly beautiful rendering of Lorre Wyatt's "Somos El Barco/We Are the Boat"; and a powerful Near/Gilbert duet that kicks off with Marvin Gaye's "What's Going On," segues to Near's "'Foolish Notion" and concludes in emotional counterpoint.

RONNIE GILBERT -- "The Spirit Is Free" (Redwood RR408) and "HARP" (Redwood RR409); Gilbert and Holly Near appear Friday at Lisner Auditorium.