Watch the von Trapp great-grandchildren sing an impromptu concert

Their performance of "Edelweiss" was apparently a complete surprise to those who heard it.

Watch as the youngest members of the singing von Trapp family break into an impromptu performance of “Edelweiss.” The song was featured in the 1965 film of the Rodgers and Hammerstein show, The Sound of Music, about their family’s flight from Nazi-occupied Austria.

The video, which was recorded several years ago, features four grandchildren of Kurt von Trapp (actually named Werner in real life), known as the “incorrigible one.”

Until 2016, the four (Sofia, Melanie, Amanda and August) were part of a singing group, The von Trapps, which carried on the tradition of the legendary Trapp Family Singers. Their great-grandfather was Georg Ritter von Trapp and their step-great grandmother was Maria von Trapp, played by Christopher Plummer and Julie Andrews in the movie.

This video, filmed at a production studio in Ohio, captures the group breaking into song for the benefit of the staff.

After the video received over a million views on YouTube, this message was posted by someone who witnessed the impromptu concert:

“These ‘kids’ showed up at the office where I work in Columbus, Ohio, sang for our staff out of the goodness of their hearts … this was completely an impromptu performance. I work for a video production company … Someone grabbed a camera and shot this thing,” read the comment. “The von Trapp great-grandkids don’t even know this exists on YouTube. I don’t even know how to get a hold of them. They were extremely humble and lovely people,” it said.

The von Trapp family settled in Vermont after fleeing Nazi-occupied Austria, after Georg von Trapp refused to sing at Hitler’s birthday party and declined to accept a commission in the German Navy. In Maria’s 1955 book, Around the Year with the Von Trapp Family, she chronicles their life on the road, and how the large family remained grounded in the Catholic faith.

In the book, we learn that the von Trapp family attended three Masses for Christmas, as they had in Austria. Read more about the von Trapps’ Christmas traditions here: