Katharine McPhee and David Foster return to the stage for first performance since their son's nanny's death

Paul Archuleta/Getty Images David Foster and Katharine McPhee

Following the tragic death of their family nanny, Katharine McPhee and her husband, David Foster, returned to the stage this week.

McPhee recently performed a duet with her her former Waitress costar Erich Bergen, while Foster accompanied the singers on piano. Dressed in all white, they took on the classic Frankie Valli song "Can't Take My Eyes Off You."

Bergen posted a carousel of videos to Instagram, including a snippet of the duet. "Singing Frankie Valli and the Four Seasons songs in Italy just seems appropriate," he captioned the post, tagging McPhee, her husband, and others who joined them on stage.

The set came several weeks after McPhee pulled out of performances for Foster's Hitman Tour to deal with what she called a family emergency. The intimate concert series features Foster sharing the stage with a revolving lineup of vocalists while he plays piano. His wife was a staple of the tour but was absent from its Indonesia shows.

"Dearest Jakarta fans, it's with heavy heart I announce I have to miss our final two shows of our Asia run," the 39-year-old American Idol alum wrote in early August. "David and I have had a horrible tragedy in our family and at least one of us needs to get back home to our family."

The tragedy in question was revealed to be the death of Yadira Calito, the nanny for their young son, Rennie. Calito died in the hospital from blunt trauma after an elderly driver accidentally accelerated into a Toyota dealership where Calito was a customer. Two other people were injured in the Aug. 9 collision, but they survived. The investigation is ongoing, and no arrests have been made.

Foster's tour is currently scheduled to resume on Nov. 1 at the Andiamo Celebrity Showroom in Warren, Mich.

Sign up for Entertainment Weekly's free daily newsletter to get breaking TV news, exclusive first looks, recaps, reviews, interviews with your favorite stars, and more.

• Katharine McPhee and David Foster's family nanny identified as victim in fatal crash

• Katharine McPhee was a clue on Jeopardy but says even she wouldn't have gotten the answer right

Smash actor Jack Davenport really wants the live Bombshell musical to run on Broadway