How sweet the sound, indeed! A-list power couple Nicole Kidman and Keith Urban visited the Monash Children's Hospital in Melbourne, Australia, last Friday, June 13, where they partook in an impromptu jam session. There, the parents of two, flanked by patients and admirers, sang "Amazing Grace."

Urban, 46, kicked off the touching performance by playing the guitar. His statuesque wife, also 46, standing a few feet away, accompanied the American Idol judge on vocals. At one point, the two sang to each other as they smiled.

After their hospital visit, the couple attended the Swisse Celebrate Life Ball. In an interview with the Melbourne Herald Sun, Kidman said philanthropic work is "one of the most important things I do." Added the Grace of Monaco actress: "I have been doing it since I became well-known in the movie industry."

Along with her charitable work, Kidman has also picked up the role of doting wife of one of country music's biggest stars. "I pretty much know every word, to every song," she told the paper of Urban's hits. "The only thing I can't do is sing and play guitar… so that is a slight problem!"

Kidman and Urban will celebrate their eighth wedding anniversary next Wednesday, June 25.

Watch their performance above!