Though there's only one title, Thunder Knocking on the Door, on the marquee outside, there are two distinctly different shows fighting for control of the stage of the Minetta Lane Theatre.

The first is a fascinating, highly conceptual play, written by Keith Glover. It examines the mythic connections between ancient Egypt and 1966 Alabama, and how control of the one-of-a-kind music known as the Blues has been passed down, from interpreter to interpreter, a musical history that has never been consigned to paper.

The other is an almost ineptly arranged song cycle. Despite a few attractive tunes by Keb' Mo', Anderson Edwards, and Mr. Glover, it doesn't really tell a story, but rather uses any excuse it can find to show off the powerful voices and personalities of its cast of generously gifted performers. These performers - Leslie Uggams, Chuck Cooper, Peter Jay Fernandez, Marva Hicks, and Michael McElroy - give it their all, but can't make sense of this mish-mash.

It is a shame that director Oskar Eustis wasn't able to meld more of a real show out of elements that are present here. There are plenty of good ideas, and the show's prologue suggests a show brimming over with invention and musical dramatic know-how. It presents a "cuttin' contest" between two men fighting for the very soul of the Blues, Jaguar Senior (Cooper) and the Trickster (Fernandez).

It is in this number that the mythic and music precepts for the show are laid down, and the song, the set (Eugene Lee's striking multi-leveled playing space, featuring an enormous two-dimensional pyramid at its center, standing seemingly in the exact center of the Nile and Mississippi River deltas), the lights (Natasha Katz), and performers seem perfectly in sync, promising a rollicking good time.

Even the following number, "This House Is Built," ostensibly covering a scene change, suggests a serious form of musical storytelling. That image is quickly dispelled with a pallid, predictable book scene, leading into a string of songs shoehorned into the story on the tiniest threads possible. The arrival home of Jaguar Junior (McElroy), for example, is reason enough to stop the show dead long enough for the cast to sing "Big Money," though it says little about Jaguar's character before or after.

The score and the story seem to coincide again near the middle of the evening, when the Trickster, now in the guise of the mysterious Marvell Thunder, challenges the blind Glory (Hicks) to another "cuttin' contest," restoring her sight, but threatening to take it, and two valuable guitars, away should she lose. Just as it seems the show is, after all, destined to become as interesting as its premise suggests is possible, the second act begins, bringing with it a collection of musical numbers more extraneous still, and a conclusion so laughably conceived and executed, the earlier promise of the show seems to vanish before your eyes.

Indeed, at the end of the evening - which runs heavily bloated at almost two hours and forty-five minutes - you're likely to remember none of the tunes, but walk away remembering how good the cast sounded singing them, and the possibilities that could have been exploited to create an integrated, cohesive musical.

Perhaps the most telling moment of the evening is Ms. Uggams's one solo, "Willing to Go," only minutes before the end of the show. It's a torch song, of sorts, sung primarily while she's sitting in a window frame. Barely derived from the plot, Ms. Uggams seems to sing it only because it's the kind of song you'd expect (and want) her to sing at that point.

There's a place for that logic in musical theatre, even today. But the show containing it has to support and embrace it, rather than use it when it wants to and abandon it at other times. Thunder Knocking on the Door could have succeeded at whatever type of musical it was trying to be, but it never found out what kind of musical that was.

Thunder Knocking on the Door
Minetta Lane Theatre, 18 Minetta Lane
Tickets online: Ticketmaster