Richard Alston Dance Company, Derngate, Northampton

Richard Alston's Slow Airs Almost All makes dancing look irresistible. It's not something I'd expected from Alston, though he's one of the most respected choreographers in Britain. His dances are intelligent, well-crafted, sometimes unduly sober. Anything that well made must be wholesome, but isn't necessarily fun. Here he looks caught up in his music, energised as well as thoughtful.

The music is Mozart's Six Adagios and Fugues for string trio, played onstage by the musicians of Stringfactory.

Alston's dance looks spontaneous because its musical impulse is so clear. Dancers dip down to a beat, or tilt deeply sideways, and the impetus sends them skimming across the stage. A turn can last a whole musical phrase, modulated by curving arms.

Mozart's fugues are arrangements of Bach. Alston sets them for a female corps. His patterns are intricate and sometimes bold: the women will stop for a full phrase, with lifted arms and squared elbows.

The adagios are set as duets, gravely beautiful and often playful. The women, especially, have little wriggles of the hips, turns of the wrist that look almost improvised. In the last duet, a woman turns into her partner's arms as if to start a waltz. The image is exactly right: these duets have the shared sweep and freedom of traditional couple dances.

The evening opened with Martin Lawrence's Grey Allegro - the first time Alston's company has performed another choreographer's work. Lawrence has danced with Alston since 1995, and his dances have Alstonish qualities: tilts of the body, lively feet, attention to music.

Grey Allegro is danced to Domenico Scarlatti keyboard sonatas, well played by Jason Ridgway. Lawrence will rattle along with the music, then stop to examine it. One couple stop well before the end of a phrase, holding still as the music slows down around them. One solo has fast allegro footwork, step for a note, leaves the notes for a long jump, rushes to catch up again.

Alston's new Overdrive fights against the repetitions of Terry Riley's Keyboard Study #1. The choreography bounces off Riley's insistent rhythms, not his melodic building blocks.

It's a large-scale piece - 11 dancers - and feels bigger for the impact and energy of its unison dances. Different groups (dressed in red, grey and red/grey by Jeanne Spaziani) move in counterpoint, then rush together. A final sequence sets the whole company dancing, then pulls the dancers offstage line by line.

Alston gets a lot of human variety from Riley's relentless clatter. In one solo, set tightly on the notes, a woman lurches off-balance and scampers to stay upright. Martin Lawrence flies in and out of the piece, twisting fluidly against the music.

Even so, Overdrive is restricted by its music. Alston uses Riley as a springboard, but doesn't quite escape those endless repeats.