The Nightwish headman told the Finnish News Agency (STT) that the letter on the band´s website contained everything necessary about the parting of ways.
"A Nightwish book will be launched in May. In it, the reasons of the separation will be examined in more detail," Mr Holopainen said.
He added that he and Ms Turunen had not spoken since the letter was posted.
"I have not spoken with Tarja, but then again we have not spoken with each other for many years."
"We all know that personal relationships are the most difficult thing in the world. All couples have their problems, and after all, there are five of us in this band."
Mr Holopainen did not wish to comment on who the new singer might be.
/STT/