Concert Is a Roaring, if Not Quite Timely, Success At the official starting time for the Jay-Z concert Thursday night, the Barclays Center in Brooklyn was more than half empty. The cognoscenti seemed to know that Jay-Z does not begin his raucous act until 9:30 p.m., not 8. But a reporter sent to see whether there were any empty seats at Jay-Z's sold-out run (and whose last pilgrimage to a true rock concert was in the late 1970s to hear Jerry Garcia and the Grateful Dead) was not among the cognoscenti. Many fans did not even bother getting on the subway until 8:30 or 9. While they waited, the Jay-Z fans wandered the arena's halls and concession stands, sampling the iconic Brooklyn specialties like Nathan's hot dogs and Junior's cheesecake, and almost inevitably downing the food with a plastic glass of beer. Many of the beers gradually made their way into the arena, where a D.J. was repeatedly flinging adjectives about acts banned by Leviticus and Deuteronomy. But it all cheered the crowd. The D.J., from the hip-hop radio station Hot 97, also tried other ploys to rouse the young crowd, which did not need that much rousing, calling out the names of boroughs and neighborhoods that spectators might hail from or their astrological signs and asking people to cheer or stand up. "White people stand up," he screamed at one point. Black people stand up. The crowd, a checkerboard of white, black, Latino and Asian, was glad to oblige, and cheer. It was a kind of casual racial bonhomie that might not have been as evident at rock concerts of tenser periods long ago. "I feel good being a Brooklynite," said Brenda Baldwin, a 54-year-old nurse. She was sitting next to me, the only near-contemporary to this 67-year-old reporter in sight, but she has been a Jay-Z fan for more than a decade. She told me she was delighted there was now a major arena in Brooklyn, the first since the demolition of Ebbets Field after the departure of the Dodgers following the 1957 season. "It's right here in Brooklyn," she said. We now have a place for entertainment. I don't have to go into Manhattan. I can wait for everything to come right now in Brooklyn. By 9 o'clock, the seats were still one-third empty, and cynics might have been forgiven for dismissing the 19,000-seat arena's claim that Jay-Z had sold out all eight shows. They would have been wrong. In the next half-hour, hundreds of fans, responding to text messages, e-mails and Twitter messages from friends, started pouring into the empty seats. When Jay-Z finally emerged on stage, spotlights grazing the crowd, the noise at shattering levels, there was scarcely a seat to be had.