"The trial will open on October 17 in an Istanbul court," Meltem Akyol told AFP, adding that Say, 42, would attend the hearing.

The multiple award-winning artist, who is a culture ambassador for the European Union, drew the ire of conservatives in Turkey with a series of provocative tweets about Islam.

He said in April in an interview with the Hurriyet daily that he felt completely ostracised by Turkish society since he declared that he was an atheist and that the criticism he had received had highlighted a growing culture of intolerance.

"I think it's time for me to move to Japan," Say told the daily.

"When I said that I was an atheist, everyone insulted me and the legal authorities jumped on everything that I wrote on Twitter. I am perhaps the first person anywhere in the world to be the object of a judicial inquiry for declaring that they are an atheist."

A senior lawmaker for the ruling Justice and Development (AKP) party, Samil Tayyar, has called Say a "son of a whore" and the composer now fears that he could end up behind bars.

"If I am sentenced to prison, my career will be finished," he said.

Turkey is an officially secular country but the AKP, which has been in power since 2002, has strong Islamist roots.