Question

What is the Rabbi’s opinion regarding songs composed by Christians for their church or for their prayer services?
A substantial part of classical music falls under this category.

And the question has several variables:

1. Is there a difference whether one listens to it for enjoyment or in order to study the piece for work / a career, etc.?
2. Is it different if this is the original recording—played inside a church—or a later studio recording, etc.?
3. What if the composer was a well-known Christian, but it is not certain whether a particular piece was actually composed for the church?
4. Are the title or the words of a song (words from Psalms, etc.) an indication and sufficient reason for it to be considered an ‘idolatrous song’?
5. Is Christianity at all still considered ‘idolatry,’ such that the songs would be forbidden in some way? (I saw that Rabbi Moshe Feinstein forbade such songs..)
6. Does listening to / watching the funeral of the English monarchs or the coronation of kings, which is a church ceremony, mean listening to their songs and choirs, and is that a problem? (Perhaps there is a leniency based on the law that ‘a person should always run to greet kings of the nations of the world’—for which even a priest is permitted to traverse a burial-field impurity zone because of this?)