But soon after they began regaling passengers with their rendition of Prince's song “Kiss”, another voice added itself to the mix.
As it happened, Maltese musician Ozzy Lino was sitting on the same train and joined in with an incredible spontaneous solo.
The two women had only met that day at the Frankfurt music fair, Gouder told jetzt.de.
“On our way to back to the hotel we were in a flow and just kept on playing in the train. Then this guy sitting there just joins us - incredible,” she said.
Within a few days the video, which was uploaded on Friday, got over 25 million views on Facebook and over 100,000 views on YouTube.
“I've just been staring at my screen and I can't believe it,” Gouder said. “It's madness, totally absurd.”
by Raphael Warnke