David Brubeck performed at the then-named Orange County Performing Arts Center in 2001. (FILE PHOTO / December 12, 2012)

One day in my high school philosophy class, the teacher gave us a list of different methods of expression and asked us to determine which ones constituted language. Among those that ended up in the "no" stack was music, since, we decided, it worked on a subjective level and couldn't relay concrete messages.

No doubt we were right. But even if music doesn't count as language per se, there are moments when it comes close — for example, the night when late jazz great Dave Brubeck visited the Orange County Performing Arts Center two days after 9/11.

That night, Brubeck brought an audience to tears playing a song on the piano. The song, "Nobody Knows the Trouble I've Seen," does have words — it's an old spiritual built around the refrain "Nobody knows the trouble I've seen / Nobody knows but Jesus / Nobody knows the trouble I've seen / Glory hallelujah" — but Brubeck, who died last week at age 91, didn't sing them that night.

Instead, he played the tune unaccompanied, and according to the Daily Pilot's account at the time, it elicited audible tears from the near-capacity crowd. Did they weep because they remembered the words, or did the melody itself have that swaying power in the days after the terror attacks?

Maybe both.

"I think, in the selection of that particular number, that he really did express for the audience some of their anguish," said Aaron Egigian, senior director of music programming for the center, which is now the Segerstrom Center for the Arts. "But each line, each verse of the song ends in 'glory hallelujah.' In a way, it acknowledges that 'I'm hurting, and we're all hurting,' but that we affirm life.

"We say, 'We will go on no matter what.' So that was the sort of nonverbal subtext, and I think that was why it hit people between the eyes and in the hearts."

I hadn't heard the story of Brubeck's post-9/11 appearance until Egigian described it in a posting on the center's blog shortly after the pianist's death. Afterward, though, I checked the Daily Pilot's archives and found that he hadn't been the only one stirred by the performance. Reporter Jennifer K. Mahal, reviewing the show, waxed almost poetic describing the scene.

"The unthinkable events of Tuesday have made the arts insignificant in comparison," she wrote. "It's hard to think about enjoying yourself, or even smiling, with images of the World Trade Center collapsing and the Pentagon burning stuck in your mind. But arts can be a solace, an emotional outlet, a window, a place to find humanity, a way to reconnect."

Mahal, who noted the "sniffles and sighs" in the audience, called Brubeck's appearance a blow against terror itself: "The goal of any terrorist is to strike fear in someone's heart. To keep them from being able to function. To keep them on the edge. To keep them from joy. The people who journeyed out to the Orange County Performing Arts Center's opening did more than just see a wonderful performance. In a small way, they sent a message — the show will go on."

That show, in fact, went on under frenetic circumstances. Brubeck and his quartet had been scheduled to perform three nights in Costa Mesa, but with air traffic halted after 9/11, the other band members found themselves grounded in New York. According to Egigian, Brubeck's representative wanted to cancel the show, but Egigian asked that the performance continue regardless, and Brubeck whipped out his cell phone and put together a replacement band in time for the performance.

Brubeck had played two earlier engagements at the center, and the staff there had even inducted him into its Jazz Society, a hall of fame of sorts for jazz greats. For the September 2001 shows, Egigian and his team decided on an intimate setting in Founders Hall, with the quartet playing against one wall and the audience seated around them.

In a tight venue like that, you hope for intimacy in the best sense, a sense that the performers and audience are sharing — or even creating — a moment together. Moments like that don't always show up in a performer's obituary, at least not in the national media. But for those who witnessed them, they can be the truest testament to an artist's power.

"I was really gratified that he just was so open to it," Egigian said Monday. Then, maybe not aware, he slipped in a jazz metaphor: "And I think it was important to him as well to not miss a beat, basically."

Features Editor MICHAEL MILLER can be reached at (714) 966-4617 or at michael.miller@latimes.com.