The Feld Ballet's second program at Wolf Trap Tuesday night opened auspiciously with two more ballets in the cycle Feld has been making lately to the rhythmically obsessed music of Steve Reich.

It's wonderful to see the formal and emotional diversity Feld achieves among the separate works of the cycle. "Medium: Rare," seen on Monday's program, is a trickily gymnastic male solo using a trampoline and eight ramps to amplify the movement possibilities. "The Grand Canon," on Tuesday's bill, uses eight dancers (four men and four women) and the eight ramps of "Medium: Rare," but not the trampoline. "The Grand Canon" is set to Reich's "Eight Lines" (originally, in 1979, an "Octet," later arranged for chamber orchestra), music that has attracted such other choreographers as Jerome Robbins, Lucinda Childs and Lar Lubovitch.

Where "Medium: Rare" is briskly athletic, "The Grand Canon" suggests some mesmerizing oscillation of the natural world, such as surf washing up and back on a beach. Each wave is much the same as the last, yet no two are identical in force or shape, and over the long haul, by minute degrees, the entire wave front changes in profile. So it is in "The Grand Canon" with Reich's music and Feld's choreography, which share a feeling of hypnotic surge and gradual metamorphosis.

The title, typically for Feld, is a sort of pun, open to several interpretations. The literal meaning refers to the structural principal of canonic imitation -- repetition in overlapping layers -- which underlies this and many other works of art.

The hint of "Grand Canyon" is reflected in the valley-like space the dancers invade between the columns of ramps at the sides of the stage. There's also an evocation of a cannon's firing in the forward propulsion and instant recoil that mark so much of the choreography.

The piece, again typically for Feld, is rich in memorable imagery. There are the curling torsos of the opening section; a line of dancers folding and rising, giving a fascinating effect of erasure and double-exposure; the runs, jumps and spins up and down the ramps in successive echelons; and the final circulating cluster of dancers, like an agitated whirlpool.

"Echo," new this year and heard Tuesday night in a tape by Reich's own ensemble, is set to "Music for Mallet Instruments, Voices and Organ." This one is another solo -- a 17-minute tour de force for Cheryl Jones. But now the atmosphere is that of a Near East fable, as indicated by Willa Kim's beguiling costume, a halter with bare midriff, filmy harem pants and tinsel-like filaments that adorn Jones' arms and hands like running sparks. Jones' supple, curvaceous, beautifully sustained performance is languorously erotic, yet never for an instant meretriciously so.

Unlike the other two Reich pieces seen at Wolf Trap, "Echo" uses no props, but in a sense there's an invisible ramp. Jones' sultry, repetitive zigzag advance downstage at the work's beginning is a startling "echo" of "La Bayadere" -- it's the celebrated entrance of the Shades reduced to a single temple dancer. Other aspects of the solo -- the flame-like wreathing arms and intertwined legs, the rippling spine, the voluptuous stretches -- mirror the exotic divertissements that spiced other 19th-century ballets, such as the "Arabian" variation in "Nutcracker."

For a change of pace, the company gave us "Intermezzo No. 1" (it was called simply "Intermezzo" until Feld created a sequel last year, titled "Intermezzo No. 2"). This neo-romantic piano ballet to music by Brahms has been one of the troupe's most endearing staples since 1969. Enhanced by pianist Peter Longiaru's warm reading of the score, it was given an inspired performance by Christine Sarry, Timothy Cronin, Judith Denman, Thomas Lemanski, Cheryl Jones and Antonio Sousa.

The evening ended with the 1982 "Straw Hearts," set to turn-of-the-century waltzes and polkas for piano, cornet and other brasses. Like MacMillan's "Elite Syncopations," which it vaguely resembles, "Straw Hearts" is a period piece that's also a spoof of period pieces. James Sewell gives an appealing performance as a Chaplinesque suitor, complete with waddling walk and twirling cane, and Theoni Aldredge's summery costumes are charming. The ballet is pleasant, clever and fitfully amusing but the length is exorbitant and the level of invention notably uneven.

Like every choreographer, Feld has ups and downs, but his average is indisputably higher than most, and he keeps on finding new twists and new terrain. Let's hope we don't have to wait as long as last time for a next visit.