Frogprince, I understand the rationale for Orthodox religious music being entirely vocal is that instrumental music was considered to be something secular that tends to evoke a kind of emotionalism and is foreign to the Orthodox spiritual life. That seems perfectly understandable to me. I don't think there is any suggestion in Orthodox Christianity that secular instrumental music is wrong, simply that it is not appropriate for religious music. Both Russia and Greece have strong traditions of instrumental music which surely could not have existed had the church disapproved.

That is entirely different from the view that all instrumental music is forbidden.