“Push the button,” goes one refrain of the relentlessly button-pushing musical “The Color Purple.” Audiences who prefer not to be whipsawed between pure virtue and despicable evil should steer clear of this superheated show at the National Theatre.

The musical’s heart-tugging tactics are blatant and persistent, but that doesn’t mean the affair is entirely unskilled. Adapted in 2004 from Alice Walker’s popular 1982 novel, which was set mainly in rural Georgia during the first half of the 20th century, the show juxtaposes the unbearably brutal with the intensely sentimental. The men are simple violent dogs and the women — especially Celie, raped by her father and reviled as “ugly” by her snarling husband — are pitiable and charismatic. When gross injustices are righted as the blues-gospel-power ballad score hits anthemic heights, even the jaded might feel free, for an instant, to tingle away.

The non-Equity cast at the National renders the extremes of this saga with commitment and flair. (Perhaps the ensemble is relieved to be in one place for two weeks: This group played eight cities in 10 days to start the month.) The voices are sure and the bodies are generally limber, with the performers hitting a jubilant peak during the raunchy blues and snake-hipped dancing of the big juke-joint number, “Push Da Button.”

The women, of course, are especially winning. Dayna Jarae Dantzler loosens up beautifully as Celie evolves from cowering victim to self-possessed entrepreneur. Taprena Augustine glows with style as the singer and universal lust object Shug Avery, while Pam Trotter is amusingly imperious as Sofia, who dominates her husband but fights a losing battle with white Southern law. All three performers have an engaging ease with the folksy comedy and romantic stirrings of the Marsha Norman book, and vocally they’re up to the pop and blues of the score, co-written by Brenda Russell, Allee Willis and Stephen Bray.

The orchestra is thin, with just a handful of musicians in the pit, and that does as much as anything to give this touring production the whiff of decay. (Gimmicky local angle: WPGC 95.5 FM radio host Lil’ Mo is being featured as one of the church singers.) Visually, John Lee Beatty’s set, with its hazy Southern sun hovering in the background, still shifts from church to field to (briefly) Africa effectively enough with the fast-moving plot and score, though Paul Tazewell’s sharp costumes feel like the most assertive element of the design.

The “Purple” hallmark endures: the spirit that churns on as Celie gradually finds blessings worth counting. At the National, it’s a steambath of pathos, if not exactly a Broadway spectacular.

Pressley is a freelance writer.

The Color Purple

Book by Marsha Norman, music and lyrics by Brenda Russell, Allee Willis and Stephen Bray. Directed by Gary Griffin. Choreography, Donald Byrd; lighting, Brian McDevitt; sound design, Craig Cassidy. With Traci Allen, Nesha Ward, Virlinda Stanton, Deaun Parker, Phillip Brandon, Mark Hall, Edward C. Smith, Cameron J. Ross, Allison Semmes, Christopher Sams, Karen Niceley, Keyon Powers, Melana L. Lloyd and Julius C. Carter. About 2 hours 45 minutes. Through April 24 at the National Theatre, 1321 Pennsylvania Ave. NW. Call 800-447-7400 or visit telecharge.com.