Superstar singer Beyonce has serenaded a different New York City venue: The United Nations.Beyonce performed her song "I Was Here” on Friday in the UN’s General Assembly Hall in honor of World Humanitarian Day, which is Aug. 19. A music video of the performance will debut the same day.Beyonce sang in front of hundreds, including Julia Stiles, R&B singer The-Dream and songwriter Diane Warren, who wrote the song.Warren said in an interview that she initially called Beyonce’s husband, Jay-Z, and played the song for him over the phone. He quickly called Beyonce, and days later she recorded it. It appears on her album "4,” released last year.Anderson Cooper hosted, saying with a laugh: "Is this what happens at the UN every Friday night?” AP