"Are we in a singing mood?" Keith Urban asked 4,000 fans at the Grand Ole Opry Saturday night.

The singer, back home in Nashville to record his next album, was on hand to help his good friend, country music singer Marty Stuart, celebrate his 50th birthday along with country star Dierks Bentley.

As a huge cake decorated like one of Stuart's trademark embroidered jackets was wheeled onstage, Urban led the audience in "Happy Birthday."

After the serenade, Stuart thanked fans by imploring them, "Y'all come on over to the house after the show for some cake!" The crowd roared its approval.

Urban warmed up the audience by singing his smash hit, "You Look Good In My Shirt," and later gave a nod to his nearly 3-month-old daughter with Nicole Kidman, Rose, during his hit, "Rainin' on Sunday."

Stuart later joined Urban onstage. As the two friends sat down, Stuart revealed what he really wanted for his birthday.

"I saw your car parked out there in the lot," he said, referring to Urban's sleek black Bentley. "How about if for my birthday we trade vehicles?"

Urban laughed as he replied, "Sure. As long as I get to keep your John Deere license plate when we trade back."

By Kay West