Christopher Wheeldon and the modern.

To see Christopher Wheeldon's choreography performed by New York City Ballet's Jerome Robbins and George Balanchine is to know that his concept of dance is informed by some old sources. And though he draws on these sources, he pushes beyond them, stretching the boundaries of ballet in the process. His new work shows where ballet can go without degenerating into the unstructured goo that so often passes itself off as modern dance.

Last season, NYCB premiered Wheeldon's Carousel (A Dance), set to Richard Rodgers' famous music (updated here by William David Brohn). It returned this year with original leads Alexandra Ansanelli and Damian Woetzel reprising their roles. Carousel begins with its large corps de ballet moving carefully and closely in the semi-dark behind a scrim; throughout the dance, they are more of a crowd than a corps, for they do little outright ballet. Four soloists soon infiltrate the corps and set themselves apart with flashier dancing, though there is little solo work per se in the piece?the dancers are always responding to one another or moving together.

But what feels like the raison d'etre of Carousel is the pas de deux with Ansanelli and Woetzel. Here, the music loses any relation to the familiar strains of Rodgers' composition, and the corps and soloists all go offstage; it's hard to see any relation between the pas de deux and the rest of the piece. It's also not easy to divine the story between Ansanelli and Woetzel. The two have excellent chemistry, but nothing that happened in the opening section prepares the audience for their intimate duet, in which their characters clearly share a great deal of history. The break to finale is similarly abrupt; the sections don't hang together well.

Still, to watch Carousel alongside older portions of NYCB's repertory is interesting in itself. Though Fancy Free was not performed this season, Robbins' work seemed an obvious influence, especially in the men's parts. Balanchine's The Steadfast Tin Soldier, which showed directly before Carousel, is an even more remote inspiration, but there were echoes of it in Ansanelli's demure attitude, though the fluid movement of Carousel was in stark contrast to the first. Robbins' Piano Pieces, which came after, also seemed as though it could have been a factor, if unconscious, in developing Wheeldon's thinking, particularly in the opening and closing pieces, but also in the pas de deux relationships. However, the modern sensibility in Carousel called for fresher movement than one gets in the choreography of Piano Pieces. There, the purity of ballet is always a wall between the dancers, while in Carousel Ansanelli and Woetzel, though utilizing classical ballet, are better able to express their complicated passion because of the freedom Wheeldon gives that traditional motion.

Liturgy, which premiered this season, is an even more shining example of Wheeldon taking inspiration from choreography past. Sandwiched between pieces from Robbins and Balanchine, Liturgy evinces clear traces of his predecessors' dance vocabulary. In the persons of Wendy Whelan and Jock Soto, Wheeldon's choreography seems like the modern fruition of what those men and other influences like Kenneth MacMillan strove to achieve: that is, choreography that speaks a true, universal language that streams through dancers and reaches the audience undistorted. Liturgy feels like a prayer or meditation, perhaps a sacred rite, with Whelan and Soto communing with each other and the audience. The beautiful but haunting music, an Arvo Pärt composition called Fratres, gives the dancers ample room to interpret and fill in their own meanings, just as the absence of a set and the minimal costumes let the audience feel part of something mysterious. Nothing interferes with the dancers' movement as invitation for the audience, out in the dark house, to participate.

Of course, the participation is entirely mental; would that more people could dance with Soto and Whelan's incredible dexterity. Their acrobatics are breathtaking, yet don't seem contrived?in contrast to the athletic sections of In the Night, a Robbins piece that shares the bill, in which the strict ballet limits both the performers and the audience. There's less connection onstage, and no connection between dancer and viewer. The program's Balanchine pieces also made for interesting comparisons, as they showed the master's early and late stages, both extreme ends of a spectrum: the "Valse-Fantasie" feeling like something from a dance school's recital and "Le Tombeau de Couperin" verging on a cartoon of modernism.

Liturgy was a refreshing step away from those extremes, to a sinuous, mature, moody choreography. The piece appears to be plotless, though it's possible to read plots into it. The lack of a conventional story is far from harmful; as with Wheeldon's other choices, it only helps make his work feel more in tune with modern sensibilities and ways of communicating.

NYCB has a great wealth in its repertory. This season, it brought out many old favorites, including Swan Lake, the gold standard of ballets. The fact that it has an accomplished choreographer like Wheeldon is an excellent indication that NYCB can remain relevant. Carousel and Liturgy, in addition to several other new Wheeldon pieces, are evidence of a new force that builds on foundations of choreographers past while innovating and expanding on them to establish something new.