One of the world's leading pianists has surprised concertgoers by storming off stage because a fan was filming his performance on a smartphone.
Krystian Zimerman, 56, returned moments later and declared: "The destruction of music because of YouTube is enormous."
He carried on with his recital, but chose not to perform an encore and cancelled a post-concert reception.
The Polish pianist joins several high-profile musicians who have spoken out against filming.
In April, indie rock band the Yeah Yeah Yeahs put up a note for fans entering a gig.
"Please do not watch the show through a screen on your smart device/camera," it said, along with some stronger words.
Former Pink Floyd bassist and vocalist Roger Waters described filming at gigs as showing a "lack of respect" to the artist.
Agitated
Zimerman was performing at the Ruhr Piano Festival in Essen, western Germany, where he was said to have spotted a member of the audience filming the concert from the balcony.
"He noticed someone up in the choir seats filming the concert on their smartphone. We think it was probably an iPhone," said festival spokeswoman Anke Demirsoy after the performance.
"He asked them to stop, but they didn't. So he interrupted the recital and walked off stage."
Zimerman then apparently told the audience that he had lost recording contracts and projects because of recording company executives telling him: "We're sorry, that has already been on YouTube."
The festival's director, Franz Xaver Ohnesorg, said he sympathised with Zimerman's frustration.
He told German media: "What happened is theft, pure and simple. It cuts particularly deeply when the artist is of a sensitive nature."
The BBC could not reach Zimerman on Wednesday for comment.