Gwen Stefani, Pharrell sing 'Hollaback Girl' on 'The Voice'

LOS ANGELES, May 7 (UPI) -- Gwen Stefani visited the set of The Voice on Monday to get a feel for the reality show for which she is slated to be a judge soon.

The singer performed her 2004 hit Hollaback Girl, welcoming the co-writer of the song, Pharrell Williams, up on the stage with her.

Stefani said she was excited to get to work as a judge during Season 7, which is slated to premiere in the fall.

"Two minutes ago, I was giving birth, and now I'm standing here in front of all you guys -- it's incredible!" she said.

Stefani is temporarily replacing original The Voice judge Christina Aguilera, who is taking a break for the pregnancy of her second child.