The National Symphony Orchestra, midway through its national tour, found itself facing an eager near-capacity crowd Saturday night in Seattle's spanking new concert hall. The musicians, making their first visit to this region under Music Director Leonard Slatkin, came just in time to get a taste of the Pacific Northwest's moody climate.

The orchestra has been traveling with a repertory heavily weighted, as one might expect, toward American composers, though each presenting organization has had the option to select from a menu also including Haydn's Symphony No. 67, Mozart's Concerto for Two Pianos, Stravinsky's "Oedipus Rex," Elgar's Symphony No. 3 and Slatkin's own compilation of various arrangements of Mussorgsky's "Pictures at an Exhibition."

Seattle decided on an all-American program. Saturday night's concert also marked the first time the NSO has been heard in the Seattle Symphony's acclaimed new home, the 2,500-seat Benaroya Hall, which opened a little more than a year ago. The building is an aesthetic jewel, with a sleek facade of airy glass panels, Minnesota limestone and aluminum.

Cyril Harris (who designed the original Kennedy Center Concert Hall sound) has clearly scored a success with his acoustical design for Benaroya's Taper Auditorium. The sound definition tends to emphasize brightness over bass but remains remarkably even and focused from any vantage point. By concert's end, the NSO collectively expressed pleasure by enthusiastically stomping their feet after Slatkin thanked the audience for sharing the "magnificent new hall."

Saturday's program consisted of Samuel Barber's Second Essay for Orchestra (Op. 17), the Sixth Symphony of William Bolcom, George Gershwin's "An American in Paris" and Aaron Copland's Symphony No. 3. Things commenced on an alarmingly tentative note in the Barber with a couple of flubbed entrances as the players evidently adjusted to the hall's brightly responsive acoustic. Because of the piece's epigrammatic intensity, the recovery time seemed magnified, and one could sense the audience holding its judgment in suspense. But thereafter it was mostly smooth sailing, with the orchestra settling into a confident mode that swiftly became infectious.

Some exaggerated attacks of percussion and brass aside, Gershwin's musical postcard was given a sparkling, extroverted account, with Slatkin molding the wailing bluesy nostalgia theme into luscious curves. Elisabeth Adkins, who has been filling in on the tour for ailing concertmaster William Steck, etched the brief violin solos with a lingering beauty.

The Gershwin made a telling complement to the Bolcom Sixth Symphony, which also incorporates popular idioms, albeit within a larger fabric that Bolcom labels the "most brooding of my symphonies." The NSO commissioned the work--underwritten by a Hechinger grant--and premiered it in 1998; this was its first performance in the composer's native Seattle. Bolcom is routinely labeled an "eclectic" composer, and indeed the symphony embraces a freely used 12-tone row and Mahlerian anguish, with alternating movements that quote respectively from the '20s hit songwriter Vincent Youmans and Schumann's "Carnaval."

Yet clearly there is a deeper vision at work. What's less clear is how to take the symphony's jolting gear shifts into the F. Scott Fitzgeraldesque Youmans tune in the Burlesk and the nose-thumbing finale titled "Marche II Contre les Philistins." Just a species of postmodern irony? The finale in particular feels clipped and disproportionate after the emotional weight of what has preceded.

The contemporary rebirth of interest in the symphony as a viable form has its parallels with the late '30s and '40s, when American composers sought a larger, epic expression, perhaps partially in response to the country's newly emerging international status. The most enduring result is without question Copland's Third Symphony, his largest orchestral work, completed in 1946. Critical reception has always been mixed, with some finding a rhetorical overreaching alongside passages of great beauty. But on this evening the experience was of a profoundly convincing masterpiece.

It was very moving indeed to observe the NSO in top form for the Copland--the score calls for virtuoso work from every section of its augmented orchestra--with a richer blend of string ensemble than I recall (not having heard these musicians for more than a year), along with gut-punching brass and percussion and memorably sprung wind solos. Slatkin seemed to allow the players greater flexibility of expression than is his wont, yet he pulled it all together with thrilling cohesion. His brisk tempo in the middle of the first movement highlighted the symphony's dialectic of strife and serenity, while the elegiac opening of the third movement haunted like the post-Civil War allegories painted by Winslow Homer. By the time Copland's spirit of New Deal optimism triumphed in the final climax, the audience sprang to its feet in a rush of enthusiasm.

The tour will head south into California with performances in San Francisco, Sacramento and Irvine.

CAPTION: Leonard Slatkin, shown in 1998, led the touring NSO Saturday.