I would assume music praising Satan.
is it true that tricks like masking the satanic chants and words or playing them backwards are used?
I suppose it’s possible, but why make the effort when you can sing about Satan in the lyrics
how does listening to such music affect us spiritually?
It only does if you let it. If someone is strong enough in their faith, it shouldn’t matter. It’s just an excuse like violence in the media makes people commit violence. It’s the person’s fault, not the music, TV, movies, games, etc.
is there a proper christian website dedicated to such music or such bands where we can know about the satanists?
I’m not sure about bands, but it’s pretty easy to look up information about Satanism. Keep in mind, not all Satanist are anti-Christian or worship Satan as a deity. In fact the cults that do I believe are in the minority.
on a more specific level, are instrumental bands like enigma or deep forest satanic?
Nope, they are instrumental bands.