In a season filled with new and original holiday shows from the region's professional theaters, you'll find some with a more traditional sugarcoating than Delaware Theatre Company's A Cappella Humana, but I doubt you'll find anything more inventive.

This retelling of the nativity in modern terms, with three Magi guided by a star only after their GPS conks out, links the story through the ages and is especially effective in Kevin Ramsey's staging of a cast with wide-ranging singing voices and a smooth upper register when they sing as one.

Ramsey, whose work is a staple at Delaware Theatre Company, created A Cappella Humana and, along with his niece, Pearl Ramsey, wrote the book for the show. It is, until it takes a dive in the last part, a holiday treat but not a confection - the highest-concept Christmas show I can remember seeing. The nativity, and the story beyond it, is told as a reality TV show, which sounds cheesy but in the Ramseys' creation has pertinence.

In one scene, people send text messages to one another as we read them on two of three screens that cover the walls of the stage; in others, they tell pieces of the story as regular people thrown into the plot, and are interrupted by the strains of their everyday lives - or by a commercial.

There's something oddly transporting about all of this, as if we're in a time machine that hasn't quite left but moves us backward even so. And it's highly spiritual, laden with traditional, sacred, and gospel numbers, and even a piece by Kevin Ramsey about taxes, which figure largely in the story then as now. You could call A Cappella Humana the first liturgical jukebox musical.

Too bad, then, that it goes awry so suddenly. A Cappella Humana offers its surprising, impressive little twists through the first act and some of the second, then loses control of its steering. In a quest to develop tension and deliver messages about the differences in what we strive for and what we actually do, the show turns so heavy-handed in its last 20 minutes it's like being forced to take medicine.

The pummeling morality message left me exiting the theater cold; it wasn't until I thought about what I'd seen for the 90 minutes before A Cappella Humana stumbled that I could again appreciate the show's striking ingenuity.

Master musician Daniel Delaney backs the cast commandingly on cello, a pleasure to hear as the only accompaniment generally on stage beside Chesney Snow's excellent mouth-percussion, Bobby McFerrin style. Snow plays the "Little Drummer B-Boi." Mykal Kilgore is wonderfully appealing as Emmanuel - read that as God. Katie Zaffrann is a Mary concerned with her makeup, Clinton Derricks-Carroll is a bewildered Joseph, and the Magi are Daniella Dalli, Jannie Jones, and David Marmanillo.

They know how to raise a joyful noise. A Cappella Humana is a world premiere, and it will probably, as they say, have legs. If its own joyful noise is smoothed out through the ending, those legs could be strong, indeed.

A Cappella Humana

At Delaware Theatre Company, 200 Water St., Wilmington, through Dec. 18. Tickets: $35-$49.

Information: 302-594-1100 or www.delawaretheatre.org.

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Contact staff writer Howard Shapiro at 215-854-5727, hshapiro@phillynews.com, or #philastage on Twitter.