Could any decent human being not feel for the besieged, homesick GIs of "One Red Flower"? The answer, unfortunately, is yes. This new musical about a year in the life of an Army platoon in Vietnam wants you to commune deeply with the wartime experiences it memorializes. Perversely, though, it withholds an ingredient that should have been fairly easy to supply: an American fighting man to care about.

Based on actual letters home from soldiers on the front lines in Vietnam, "One Red Flower," with its timely themes, possesses obvious curiosity value. The Signature Theatre production has other things in its corner, namely a striking staging by director Eric Schaeffer, a cast of seven in polished voice and a passel of effervescent melodies by Paris Barclay that are infused with the energy of Motown and the Beach Boys.

It is difficult not to reflect on current events when the soldiers, perplexed by the geopolitics that dump them in an intractable conflagration and reeling from the death of a comrade, break into the muscularly convincing "I Don't Understand This War." Or when a terrified Army private taken prisoner by the enemy sings a plaintive aria, "Debby," to his unreachable wife.

But in spite of obvious parallels to Iraq, "One Red Flower," adapted by Barclay from Bernard Edelman's book "Dear America: Letters Home From Vietnam," never challenges the shopworn conventions of its genre. The dialogue falls into entirely predictable categories. the gung-ho imprecations of the sergeant (Joshua Davis), eager to taste blood; the musings of the overworked medic (Josh Lefkowitz), enraged by the immorality of the war; the naive longings of the enlisted man (Stephen Gregory Smith), desperate to see action.

These are the average GI Joes in a thousand other evocations of Vietnam, from "Miss Saigon" to "China Beach" to "Platoon." And if the words they speak in "One Red Flower" are more authoritative because they're from the pens of real people, this does not excuse Barclay from imbuing the characters with a comparable veracity.

The six Army men of "One Red Flower" -- a seventh character, a soldier's mother, is played by Florence Lacey -- are composites of the letter writers quoted in Edelman's book, and they feel pasted together, like cutout characters. The musical is long on stories of war -- at 2 hours 40 minutes, very long -- and short on biographical detail. The songs distill the soldiers' thoughts without telling us who they are; the score takes no revealing detours into the intimacies of personal history, the sort of specifics that allow a bond to be cemented between those onstage and those sitting in the dark.

The source material may not have supplied much context; letters to loved ones rarely do. The missives are infused with loneliness and dread and longing, but the descriptive speeches do not include much drama. (The piece has the feel of a rock recital.) If Barclay, an Emmy-winning television director ("NYPD Blue"), wants us to experience a combat death as something to mourn, he must offer more than skeletal, epistolary evidence as to what we're losing.

"One Red Flower" unfolds around the year-long tour of duty of Billy Bridges, played by Smith, a desk clerk who itches for the battlefield. The musical does not try to impose much shape on Billy's time in country -- like war itself, the show is a seesaw between episodes of ennui and horror. Billy's lucked into service, apparently, with the most genteel of platoons. Flammable issues like racism and class difference get short shrift, and profanity is kept to a credulity-straining minimum.

The show, in fact, sidesteps any kind of extreme idea or behavior. In its effort to embrace the complexity of war, it is scrupulously balanced: The hawkish characters express ambivalence about genocide and the doves acknowledge the rewards of comradeship in arms. Because so many of the characters seem to speak with more than one voice, however, it's difficult to know whether this notion is an intentional one.

You might call Schaeffer's approach to "One Red Flower" multisensory. The production begins with a nifty effect: the roar of a helicopter to rattle the seats, followed by a gust of wind, whipped by the rotor, that rolls over the audience.

Eric Grims's impressive set looks like a ruined bunker in the middle of the jungle, its central feature a screen on which Michael Clark projects emblematic images of war. The design elements, including Chris Lee's lighting, mesh breathtakingly in the musical's final tableau -- the show's most emotional scene -- when the stage is bathed in a close-up of a portion of Maya Lin's Vietnam Veterans Memorial and the names of the dead are made to shimmer as if they were blurry points of light in a distant constellation.

Barclay's score shimmers at times, too. The buoyancy of the music may not match the mood of the narrative, but it's enjoyable 1960s pastiche nonetheless. The actors add boy-band elan and harmonizing to such pleasing numbers as "My Own Dream," and "The Land of Make Believe." Smith brings winning affability to "If You Are Able," and he and Lefkowitz do extremely well by the title song (even if the floral metaphor it suggests for Vietnam tracks with nothing else revealed in the musical). The actors playing the fresh-faced soldiers are fine; Lacey is assigned the intrusive task of gold-star maternal troubadour. Through no fault of her own, the role does not supply the intended emotional bedrock. Then again, no moment of "One Red Flower" occasions a grope for a hankie.

One Red Flower, music by Paris Barclay; book and lyrics adapted for the stage by Barclay from "Dear America: Letters Home From Vietnam." Directed by Eric Schaeffer. Set, Eric Grims; costumes, Jenn Miller; lighting, Chris Lee; sound, Tony Angelini; projections, Michael Clark. With Clifton A. Duncan, Kurt Boehm and Charles Hagerty. Approximately 2 hours 40 minutes. Through Oct. 3 at Signature Theatre, 3806 S. Four Mile Run Dr., Arlington. Call 703-218-6500 or visit www.signature-theatre.org.

Clifton A. Duncan, above, and Kurt Boehm, below, play homesick soldiers in "One Red Flower," based on letters from GIs on the front lines in Vietnam.Enlisted man Stephen Gregory Smith, right, with Charles Hagerty as a warrant officer, is desperate to see combat action in "One Red Flower."