Acclaimed violinist Joshua Bell played an incognito concert at the L’Enfant Plaza Metro station in 2007 as part of a Washington Post experiment, and the world has not let him forget it. He returned to the Metro on Tuesday for a free concert at Union Station. (The Washington Post)

“Hi, does your camera make a clicking sound? You have to shut it off. He’ll hear you. And he’ll stop playing.”

It was three minutes before Joshua Bell took the makeshift stage, and his press representative was prepping the front row. The world-famous violinist always plays in almost perfect silence — in concert halls, grand ballrooms and even in palaces.

But Tuesday, for the second time, he was playing near a D.C. Metro station.

Gene Weingarten, a Washington Post writer who asked Bell to take his $3 million violin under ground for the first time in 2007, introduced Bell to the crowd of hundreds who packed the main hall of Union Station.

Back then, Weingarten explained, there were no cameras to be clicked. He hadn’t told anyone that Bell was playing. So, instead of fans arriving two hours early to get a good view, more than 1,000 commuters in L’Enfant Plaza rushed by Bell without stopping to hear the music. The popularity of the resulting story, “Pearls Before Breakfast,” is what brought so many people out to hear Bell perform Tuesday afternoon in an event sponsored in part by The Post. This time, he would play with the help of younger musicians he had mentored, in dress clothes, and although technically still in a Metro station, he wouldn’t be underground. He hoped people wouldn’t want to miss it.

Violinist Joshua Bell's hair flies as he gives a performance at Union Station. (Michael S. Williamson/The Washington Post)

He was right. The hall was so packed that when the students who accompanied Bell performed an opening set, people in the back of the crowd kept clapping after the students left the stage, not realizing that the music they were then hearing was a recording.

But when the violinist himself finally stepped out, the applause was thunderous.

“Wow,” Bell said into a microphone. “This is more like it!”

Beneath signs that read “GARAGE” and “BUS,” Bell played for just under 30 minutes. He bent and swayed with the music in the energetic manner for which he is known. The sounds of his violin and the other string instruments bounded off the high ceilings of a room through which an estimated 20,000 people pass each day. Although the noise of commuters in other parts of the station was still audible, the speakers amplified Bell’s music enough to fill the main hall. He performed three pieces: two from Bach and one from Mendelssohn. The Mendelssohn piece, Bell told the crowd, was written when the composer was just 16.

This made eyes widen in the front row, where about a dozen children were sitting inches away from Bell’s black, lace-free shoes. Some were home-schooled and some, with the encouragement of their parents, had played hooky.

“School is important,” said Regina Verow, who came from Annapolis with her two daughters, one of whom she took out of school for the day. “But this is a different kind of education.”

Bell noted more than once how excited he was to see kids there. When he played incognito in 2007, it was the children who most often stopped to listen before their parents rushed them away.

Now, it was again the kids who were the most free to show their excitement. A boy in a bright orange T-shirt clapped his hands so hard his palms reddened after every song.

“Do any of you play violin?” Bell asked the kids. Sean, age 9, raised his pink palm in the air so high that he lifted his whole body up from the marble floor.

Sean’s parents gave him his first violin at age 5, and now his younger sister was learning too. “Months and months of only ‘Twinkle Twinkle,’ ” his mom, Carolyn Dempsey, explained. Sean likes playing in the tree in his back yard and taking apart his skateboard, but he loves violin most of all. When he grows up, he plans to live in a log cabin with no electricity, sell vegetables (mostly potatoes) and play his violin all day. He doesn’t want to be as famous as Joshua Bell, because he doesn’t want people to stop him for autographs at the grocery store.

Sean does know about the time that “all those busy people” in D.C. ignored Bell, but he said he doesn’t really understand what happened.

“I guess they had to catch a Metro train,” he said. “But like, the trains come so frequently. I would have just stopped.”

“I would have stopped” and “I wish I could have been there” are what strangers always say to Bell, even seven years after his L’Enfant Plaza show. It’s part of the reason he wanted this do-over. In between discussing breakdowns on the Red Line and how they wished they were taller so they could see Bell better, people in the crowd could be heard discussing the original experiment these many years later.

“I read it and I remember thinking, man, I’m at L’Enfant Plaza all the time,” said Michael S. Piwowar, a commissioner on the Securities and Exchange Commission. He used his lunch break to meet his wife and 14-year-old son for the concert. His son, who is partially deaf, plays violin too.

Piwowar said he still wonders if he would have stopped that day. But what matters more is that now, his son is here.

“And he’ll know,” Piwowar said. “People do appreciate this music.”