The journey up from slavery for seven black women

And I Ain't Finished Yet Theater piece, with songs, by Eve Merriam. Directed by Sheldon Epps. Musical direction and arrangements by Patti Brown.

The Manhattan Theater Club is presenting a tribute in miniature to seven black women who journeyed up from slavery. The vibrant and talented Lynne Thigpen relives moments from these heroic lives in the dramatic and musical vignettes assembled by Eve Merriam. Miss Thigpen's performance apart, the results are uneven. But at its best, ''I Ain't Finished Yet'' is spirited, moving, and, in its reprise of black vaudeville, infectiously funny.

After a brief introduction, Miss Thigpen makes a quick onstage costume change to become an ex-slave clad in the traditional cotton dress, apron, shawl, and bandanna. Having delivered a matter-of-fact recital of the cruelties of family life in bondage, the actress moves on to other characters in Miss Merriam's historical-folk sketchbook. They include a victim of Ku Klux Klan rape and spoilage; Ida B. Wells, the Memphis schoolteacher who sued a Southern railroad over its segregation policy in 1885; and Fannie Lou Hamer, whose Freedom Party delegation challenged the Democratic Party national convention in 1968. (A program note advises that the show's material was taken from the Congressional Record, historical documents, autobiographies, interviews, and 19th-century songbooks.)

On the strictly entertainment side, the versatile Miss Thigpen impersonates ''Ma'' Rainey singing the blues (the actress is no mean blues singer) and offers a sampling of ''Moms'' Mabley's earthy vaudeville routines. The least effective sketch casts Miss Thigpen as preaching Sister Tessie in a rather stereotyped simulation of a black church service.

The musical members are admirably handled by Miss Thigpen and her fellow entertainers: Robin Karfo, Stanley Ramsey, and Bo Smith. The robust piano accompaniments and occasional vocal assists of musical director-arranger Patti Brown add some strong pluses to the Upstage revue directed by Sheldon Epps. At present, ''I Ain't Finished Yet,'' which runs about 80 minutes, resembles an unfinished work. Considering the appeal of the subject matter and the performing dynamism of the magnetic Miss Thigpen, the new Merriam Theater piece would seem to merit the further development that might make the sum of its whole equal some of its best parts.