Two choreographers. Two composers. Stir vigorously.

What happens when you mix two modern choreographers, both born in Australia, with two composers of different eras?

The American Ballet Theatre (ABT) is hoping that you get a modern hit, one that would give its troupe a break from the endless repetitions of "Swan Lake" and "Giselle" that make up so much of every ballet company's repertoire.

The new ballet, "Hereafter," is outsized, not only in ambition, but even in its setting. The 120 members of the New York Choral Society tower above the dancers on two-story, steel tiers, designed by Santo Loquasto.

The two-part ballet pairs the contemporary "Harmonium" by Pulitzer Prize-winning American composer John Adams with German composer Carl Orff's "Carmina Burana," first performed in 1937.

"Hereafter," which depicts the journey of one man's life, was conceived by ABT artistic director Kevin McKenzie after he heard both sung together at a concert. "One work is spiritual; one is earthy, [but they are both] about birth, death, and renewal," says Mr. McKenzie.

Interestingly, both works were also based on poems. Adams was inspired by John Donne's "Negative Love or The Nothing" and Emily Dickinson's "Because I would not stop for death" and "Wild nights." Orff composed "Carmina Burana" to 24 poems from a 13th-century codex found in a German monastery.

Because the two works are so different, McKenzie says, he thought: "Why not use two choreographers and end up with a full evening ballet that was in fact a story?"

He selected Australians Natalie Weir, a wunderkind who was offered her choreographic commission at 18, and Stanton Welch, a former soloist with the Australian Ballet who is now director of the Houston Ballet.

Ms. Weir and Mr. Welch worked separately, never consulting about the choreography. Nonetheless, says Weir, "Stanton and I have [made] similar things thematically. I don't know if that's an Australian thing, but I think it's in the music. It seems to be a journey of one's life. That seems to be very profound to both of us."

She says that when McKenzie first asked her to listen to "Harmonium," "I was blown away. It had all the drama I'm looking for."

Although their concepts were parallel, on opening night the differences in movement styles and time settings became apparent, often leaving the audience with a disconcerting welter of images.

Weir set her leading character (Ethan Stiefel) in the modern era, surrounded by people who might be found in New York's Times Square.

Of her organic choreography style, Weir says, "I don't make any of the movement beforehand. I never try to place steps on top of a dancer. I like to work with the dancers so they feel the steps belong to them."

In contrast, Welch envisioned "Carmina Burana" as a primitive ritual, like those of the Incas, and employed classical ballet technique, punctuated by bursts of movement for the men.

Before the ballet's première, McKenzie had said, "When you create a work, what you intend might have to change. I view this as a process."