Moments after Nigeria clinched its 2-1 win over the United States in today’s Olympic soccer match, Yisa Basorun slapped a trumpeter on the back and started moving his hands like a conductor.

As the trumpeter played, a crowd of more than 100 Nigerian fans clad in green and white began to shake, sing and celebrate. The Nigerian team had secured its advancement to the next round of the Olympic Games, so the music played on.

If only getting through the gate had been so easy.

When Basorun left Nigeria for Beijing three days ago, he and his band — three trumpeters, a bass drummer and two snare drums — breezed through security. But trying to get into Workers’ Stadium before today’s match was a little more complicated.

The Chinese security efforts in Beijing have been routinely praised for their rigidity and exactitude. They count every number on a passport to make sure it matches a credential. They hold tickets under a hologram microscope to make sure they’re legitimate. And they make people drink bottled water if they’re carrying it in their bag.

But Basorun and company discovered a more obscure security check custom.

When the band went to bring their instruments inside, security immediately stopped them. The BOCOG staff explained that they were worried the instruments might cause trouble. Basorun promised they wouldn’t be a problem. Just to be sure, the security staff pulled out a waiver and asked them to sign it.

Basorun has been to a handful of World Cups and two Olympics, but that was the first waiver he could remember signing to get inside.

“It said we would be on good behavior and not cause trouble,” Basorun said. “We have been going around the world with this, except here they almost wouldn’t allow us.”

Basorun said they sorted it out quickly and that the security guards had a smile on their face the entire time. That underscores what a lot of people are saying about security here in Beijing.

Tight? Yes. Effective? Absolutely. Service with a smile? Of course.

It’s that last aspect that jumps out at people when they come through security for an Olympic event. It’s all smiles and hellos.

That’s especially important in a culture that appears to follow rules to the last letter. This isn’t the U.S., where you might be able to convince someone to bend the rule. In China, if a guard is given a rule, he’ll follow it until someone in authority tells him to change.

I found that out firsthand yesterday when I tried to walk through an empty Workers’ Stadium from the west gate to the east gate. When I reached the east gate, I saw that it had a padlock hanging on it that was unclasped. I asked the guard behind the gate if I could slip out because the place I needed to go was 100 yards from where we were standing. There were maybe five people on the sidewalk outside. I figured it would be no big deal.

But he shook his head and pointed north. I shook my head and pointed south. He shook his head and pointed north. I shook my head and reached for the padlock. His furrowed brow let me know that wasn’t a good idea. As soon as I dropped my hand, he smiled and I walked away from the whole exchange slightly less frustrated as a result.

Basorun said his exchange was similar. Security pulled out the band’s trumpets and asked the Nigerians to blow them. Then, someone who spoke English said that they would prefer that the Nigerians not bring them in.

“I told them it would not be a problem,” Basorun said. “We use it to entertain.”

And entertain they did.

The band played for two hours straight. The entire time Nigerians wearing green and white afros danced and sang to a mix of horns and rhythms that sounded straight off of Paul Simon’s “Graceland” album.

And through it all a group of guards stood in the aisle and watched. They were watching less to see if the band behaved and more to prevent a swarm of Chinese spectators from coming down in the stands and taking photos.

“The people are so warm,” Basorun said, as Chinese people took photos of the band from the concourse above. “They seem to love us.”

When the game ended and the Nigerians began to dance their way out of the stadium, those same security guards formed a perimeter around the band. Hundreds of Chinese spectators lined up — three deep — behind the guards and snapped photos by holding their cameras high like paparazzi over the red carpet.

Through it all, the security staff kept the crowd back. And most of them had a smile on their face.