JVC JAZZ FESTIVAL REVIEWS; Tai Chi Precision and Constant Shading

It may come from the northern light, the emptiness of the land and the lurking Arctic chill, but a strain of musical introspection seems deeply engrained in Canadian pop. Think only of Joni Mitchell and Leonard Cohen, or of Neil Young longing for a northern Ontario town in his song ''Helpless'': ''Blue, blue windows behind the stars/Yellow moon on the rise/Big birds flying across the sky/Throwing shadows on our eyes.''

In her forthcoming album, ''Hymns of the 49th Parallel'' (Nonesuch), the singer K. D. Lang, who comes from Alberta, has collected some of the most searching ballads by Canadian songwriters, including ''Helpless,'' into a pop hymnal. And on Saturday evening as part of the JVC Jazz Festival, accompanied by the Brooklyn Philharmonic Orchestra and an ensemble that included steel guitar and accordion, she offered an entrancing preview of the album (due out on July 27) in a concert that was a musical retrospective. It was the rare pop event at Carnegie Hall where the acoustical balance was perfect.

An exceptionally disciplined performer, Ms. Lang suggests an unlikely combination of Judy Garland and Patsy Cline, reimagined from a Zen Buddhist perspective. Performing barefoot, she moves with the precision of a martial arts master. Her body language onstage is at once theatrical and stylized. The histrionic touches she applies to songs seem as calculated as maneuvers in a tai chi exhibition.

Few singers command such perfection of pitch. Her voice, at once beautiful and unadorned and softened with a veil of smoke, invariably hits the middle of a note and remains there. And on Saturday, she discreetly flaunted her technique, drawing out notes and shading them from sustained cries into softer, vibrato-laden murmurs.

On Saturday she balanced her commitment to the material with humor that involved playing with unlighted cigarettes, executing polka-like little dances, and projecting a twinkling merriment behind it all. The last time I saw Ms. Lang give a full-length concert in New York nearly four years ago, her sloppy stage demeanor suggested a growing lack of interest in performance. But everything that seemed on the verge of being lost then has since returned, and more.

As she has matured, Ms. Lang, now 42, has become a more austere interpreter. As befitting the title of her forthcoming album, Ms. Lang's approach to the songs on Saturday was devotional, and so were the plain, long-lined orchestrations by Eumir Deodato. Her choice of songs focused on lyrics with biblical imagery and diction. Besides ''Helpless,'' she sang Mr. Cohen's ''Hallelujah'' and two great ballads by Jane Siberry, ''Love Is Everything'' and ''The Valley,'' a meditation that suggests a secular interpretation of the 23rd Psalm.

Ms. Lang also performed several of her own songs, including ''Miss Chatelaine'' and ''Constant Craving,'' with similar arrangements. If the original songs weren't in the same league as the classics from ''Hymns,'' they provided a welcome counterweight to all the gravity.