Once, when John Adams was talking about his writing for orchestra, the composer paused for a few moments with a frustrated look on his face. "I work in a medium that may already be dated," he said. "The symphony orchestra really is a creation of a past time … There are a few dark days I feel like I am panning for gold in a river that has given it up."

Well, Adams would have been a heck of a '49er, because he has found plenty of nuggets in that symphonic stream (although I don't think it is close to depleted). You could argue there's some pyrite among his gold, as is the case with every artistic creator. But he has penned some of the best music of the last quarter century, including his Violin Concerto, symphony "Naive and Sentimental Music," fanfare "Short Ride in a Fast Machine" and string piece "Shaker Loops."

But the real richness here -- personified in the near-capacity crowds for two Pittsburgh Symphony Orchestra concerts of his music over the weekend -- is the credibility he has given classical music.

While contemporary composing is making a comeback of sorts with audiences, there was indeed a dark time in the mid 20th century when it seemed the connection had been permanently broken.

But Adams, the PSO's composer of the year, and others gave us a reason to be proud again of the splendor that can emerge from 100 orchestral musicians. He is a composer of our time.

He also is a composer about our time. From bombs to terrorists, earthquakes to war, current events have inspired him like they do film directors, novelists and playwrights, and more.

In a memorable pair of concerts, Adams conducted some of his newest works on the Heinz Hall stage: a symphony drawn from his opera "Doctor Atomic" and his 9/11 memorial "On the Transmigration of Souls."

"Doctor Atomic" takes place in the New Mexico desert in the final hours before the detonation of the first atomic bomb. For this instrumental version, Adams wisely chose to keep the most potent, electric music from the opera. With strident muted trumpets, nervous string runs and pounding timpani, the PSO teetered on the edge to capture the anxiety of the participants.

If the huge, crunchy chords that punctuated the score at times didn't show just how far Adams has come from his earlier use of minimalism (he is still unfairly tagged as a minimalist), then a hauntingly gorgeous setting of a John Donne sonnet, "Batter my heart," will. In the opera, the J. Robert Oppenheimer character sings it when alone with the dreadful weapon, and in the symphony, PSO principal trumpeter George Vosburgh did the honors, playing with incredible bittersweetness. This is Adams' most robust orchestral score to date, and the PSO answered his call with power and precision.

In stark contrast was the introverted "Transmigration," presented on Saturday. It is touching, but not in the sense that it moves you, but rather that you move to it.

In regard to its pre-recorded soundtrack speaking names of those killed in the attacks on the World Trade Center, I actually disagree with Adams's on-stage comment that the work has a "universal scale." On the contrary, it is pretty specifically connected to 9/11, and to New York. That makes sense, commissioned as it was by the New York Philharmonic (there's no mention of the airplanes in Shanksville, Pa. and Washington, D.C.)

But that's not a knock. Specific or not, Adams succeeds here brilliantly by creating a work of exceedingly good taste.

The orchestra plays no theme, per se, and pushes no healing on the listener. Instead, it sits back and quietly creates space for the audience to think. Images and feelings about the fateful day roamed in my head in an intense way that hasn't happened since 2001.

The combined forces of the Mendelssohn Choir and the Children's Festival Chorus sang clearly and exquisitely, articulating texts taken from news reports and missing persons memorials.

Preceding the work was a stunning performance of Britten's seldom-heard "Sinfonia da Requiem." And Friday, a bevy of soloists convened to present chunks of Adams' opera "Nixon in China," including all of Act III.

The highlight was hearing baritone James Maddalena, who created the role of Richard Nixon in 1987. But Adams often let the PSO overpower the singers, which compounded the already too-long Act III.

But what should be remembered long after is that the PSO can contribute to contemporary discourse, especially when it takes risks with extraordinary creative minds such as Adams.