Susannah Mulally (a radiant Colleen Madden) is looking for songs – old songs that have been passed down through generations of African-American women, songs that will die out, along with their rich history, if no one records them. So, on behalf of the Library of Congress, the plucky and tenacious Mulally is traveling across Texas in the 1930s, stopping at women’s prisons to record the inmates’ traditional songs that comfort them in jail, just as they sustained their ancestors who suffered under slavery.

In a dingy warden’s office, Mullaly meets her match in Alberta "Pearl" Johnson (a captivating Lynette DuPree), a prisoner who carries a ball and chain, an abiding faith in God, a healthy cynicism towards "white women in girdles" and a vast knowledge of music from the islands off South Carolina.

Through music, the two women form a tenuous partnership that provides an interesting but often disjointed storyline for "Black Pearl Sings!" onstage now at the Milwaukee Rep’s Stackner Cabaret. Part history lesson, part revival meeting and part showdown between two independent and determined women, it succeeds best as an entertaining evening of music that traces the African-American experience in the U.S. through song.

The play (by Frank Higgins) is partly based on the work of legendary ethnomusicologist and folklorist John Lomax, who famously recorded the music of many African-American men behind bars in the first decades of the twentieth century, including songs from Huddie "Lead Belly" Ledbetter. Switching the gender of the characters to women, Higgins’s story imagines the commonalities and the deep divides between such a pair; scholar and inmate, Caucasian and African-American, deeply religious and stubbornly faithless, privileged and impoverished.

There’s lots to talk about as Susannah and Pearl get to know each other, and each positions herself to get as much as she can out of the deal – Pearl will sing if Susannah locates her wayward daughter. Susannah will get Pearl released from jail, if she gives concerts to further her academic career. But whether the pair is discussing their fraught relationships with family, or the marketing of Pearl’s musical talent, the scenes feel like slim set-ups for the a capella spirituals and work songs that DuPree shares with her weathered and soulful alto.

One of the highlights of the show comes early on when Pearl, dressed in sweat-stained prison stripes, teaches the prim musicologist how to "dance nasty" while singing the childhood melody "Little Sally Walker." Colleen Madden’s delicate and lyrical soprano is juxtaposed with DuPree’s earthy, textured voice and the two have a moment of both musical and personal connection that is delightful to watch.

But there are few scenes where the women find common ground, and the repetitive structure of the narrative – Susannah cajoling, Pearl resisting and finally giving in – wears thin. Instead the audience waits for the next song – some joyful songs of praise, some call and response, and some filled with sorrow. A mixture of tradition with raw emotion, they rumble through the theater like slow-moving storms.

While the script brings up myriad of issues about sexism, racism, cultural appropriation, authenticity and playing into stereotypes, it doesn’t explore any of them satisfactorily. And despite luminous performances and able direction by Leda Hoffman, the characters remain flat.

So revel in the music – the real reason behind the play – and pay attention when Pearl teaches you the chorus of "Many Thousand Gone." You will want to be part of the concert.