The Kenshin theme song made a lot more sense to me when I watched it with the animation. Hopefully the FMA song will make some sense to me even though I haven't seen the show.
I can listen to the same songs for hours if I don't understand the language. Even if I know what they mean. I'm not sure why yet... actually, it's just for Japanese, there aren't many other languages I like to listen to. But I mostly just have ones from series I know, because I've already heard the song and seen the art that goes with it. It's like... I don't buy soundtracks for movies I haven't seen. Same thing.