When a new musical is engaged in the complicated process of trying to find its voice, an audience has to be willing to listen to some misplaced notes, to hear it speak and sing in a sometimes fuzzy-sounding chorus.

If the challenging assignment of figuring out for yourself whether sparks ignite as a score and a concept go a-courtin’, then Signature Theatre’s world premiere of “Brother Russia” will strike you as a worthwhile evening’s dedication to detective work. For its creators, composer Dana Rowe and book writer and lyricist John Dempsey, need the feedback to help them figure out what’s best about their sprawling, rock-inflected musical and to jettison the parts that frustratingly and at this point, substantially, weigh it down.

Rowe and Dempsey were the lighthearted craftsmen behind the musical version of “The Witches of Eastwick,” jauntily staged by Eric Schaeffer in its U.S. premiere at Signature in 2007. To their credit, they’ve departed here from the near-universal practice of adapting other material and tried to come up with a highly original narrative, taken from the life of Grigori Rasputin. He was the enigmatic Russian mystic who rose from the Siberian peasantry to become spiritual adviser to the doomed Czar Nicholas II and his wife, Alexandra.

They do, however, seem to reveal their own theatrical role models as the musical-within-a-musical unfolds. Stephen Schwartz’s “Godspell” and “Pippin,” Boublil and Schonberg’s “Les Miserables” and, most resonantly, Leonard Bernstein’s “Candide” at one point or another all spring to mind, as the narrator of “Brother Russia” — a bearded, wheelchair-bound older eccentric played by John Lescault — takes us back to Imperial Russia and the story of how Rasputin pursued his bloated ambitions.

Some of the pesky bumps an audience member encounters during “Brother Russia” have to do with this ill-defined character, who shares his name with the show’s title and purports to be the latter-day embodiment of Rasputin himself. Only now, those under his mesmerizing spell are actors in a ragtag contemporary Russian troupe. On set designer Misha Kachman’s rendering of a disheveled stage, the performers, variously enthralled or irritated, rehearse the account of Rasputin’s exploits and Brother Russia’s distorted version of pre-revolutionary Russian history.

All the while, Lescault’s bombastic Brother Russia lays a lot of arch, self-referential commentary on us: “Am I who I say I am? Let’s find out!” But in spite of his energetic efforts to get an audience to pay him heed, Brother Russia is an uninteresting device. (“Him again?” you find yourself asking, between songs.) The overwrought final speech devised for Brother Russia and full of musings on time and death is about as unsatisfying a way to wish us all a profound good night as a musical can muster.

Schaeffer gussies up the proceedings to some degree, punking up the look of his actors in garish makeup and costume designer Kathleen Geldard’s strident period mashups. One wonders from time to time whether the score, story and production all wouldn’t benefit from a toning down of artifice, and the creative team would concentrate more effectively on the musical’s nascent strength, in musicalizing the effect Rasputin has on those around him.

The venture certainly has the pipes for it, in the throats of show-tune powerhouse Doug Kreeger as Rasputin in his prime, and Natascia Diaz, in an evocatively mournful turn as the legend-enshrouded Romanov offspring, Anastasia. While Kreeger proves to be an effortless thrill generator in the dreamer’s anthem “Dolgaya River,” Diaz provides heft to the pulsing emotion of “Crush Me.” (They do expertly in tandem, too, singing the romantic ballad, “I Belong to You.”) The support is also bountifully there from such solid singer-actors as Rachel Zampelli, playing the bewitching witch who croons “Child of the Wood,” and the well-deployed Stephen Gregory Smith, giving courtly decadence its sleazy due in “This Is What You Call the Good Life.”

But the evening’s contrived theatrical framing is off from the start. Even seated in the second row of Signature’s main stage, the Max, I could make out only every 19th word of the title opening song. Perhaps the show beginning on a wrong aural footing made it harder to get comfortable with the work’s ongoing, warring realities.

Conductor Gabriel Mangiante’s seven-member band, whose sound is often enriched by the fine guitarist Gerry Kunkel, comes into ever-better alignment with the singers as the evening wears on. The actors convincingly step back and forward in time, but they’re far more compelling in their czarist guises. (It must be noted that the open-shirted Kreeger — whose chest hair all but gives a performance of its own — and Lescault bear no physical or even temperamental relationship to each other.)

Rowe and Dempsey certainly know have to drive a song to an infectious climax, and in its most effective moments, “Brother Russia” evinces an attractively realized musicianship. In its next incarnation, one hopes the songwriters can each acquire the eye of an editor extraordinaire.

Brother Russia

Book and lyrics by John Dempsey, music by Dana Rowe. Directed by Eric Schaeffer. Music direction, Gabriel Mangiante; sound, Matt Rowe; orchestrations, August Eriksmoen; lighting, Colin K. Bills; choreography, Jodi Moccia. With Russell Sunday, Erin Driscoll, Amy McWilliams, Christopher Mueller, Kevin McAllister, Tracy Lynn Olivera. About 2½ hours. Through April 15 at Signature Theatre, 4200 Campbell Ave., Arlington. Call 703-573-SEAT or visit www.signature-theatre.org.