Fergie says she felt part of her performance at the 2011 Super Bowl on Sunday was "pitchy."
During the halftime show, she and her hip hop group, the Black Eyed Peas, performed a medley of their songs, while Fergie also sang "Sweet Child of Mine" with Slash, former guitarist of the rock back Guns N' Roses, which spurred the hit song in the 1980s.
Some of my notes were pitchy to me," Fergie said on Dan Patrick's syndicated radio show. "That was just over the excitement. I was nervous. It was so exhilarating. That's a once in the lifetime thing. It was just so exciting."
"Axl is one of my vocal idols," she added, referring to Guns N' Roses singer Axl Rose." I've emulated him for years. I'm performed songs with Slash before. It was just fun. It's such a huge venue."
Fergie also said that she empathized with pop singer Christina Aguilera, who fumbled a line as she sang "The Star Spangled Banner," the U.S. national anthem.
"Your nerves just take a hold of you," Fergie said. "She's one of the best singers of our time and nobody can take that away from her. "
Following her performance, Aguilera issued a statement, saying: "I got so caught up in the moment of the song that I lost my place. "I can only hope that everyone could feel my love for this country and that the true spirit of its anthem still came through."
Superbowl XLV, Sunday's football championship game that saw the Green Bay Packers beating the Pittsburgh Steelers, was the most-watched program in television history with more than 111 million viewers, the Hollywood Reporter said.
Super Bowl XLIV was watched by some 106.5 million viewers last year. The series finale of "M*A*S*H," held onto the record for most-watched program between 1983 to 2010 with 106.0 million viewers.