I am not a native English speaker.
do you think you have to know the meaning of a song to have any kind of emotion?
Certainly not. The point of emotional performance is to reinforce the words, not merely to present them. If they can be reinforced with enough clarity, the reinforcement can be understood without the words.
I've listened to a lot of opera without much understanding of the words, though I always had a basic notion of the narrative. I've listened to loads of rock music where the words were utterly unintelligible or meaningless. But much of it is still emotionally powerful. Even after 50 years, I still get an emotional charge from the music of groups like Yes, and that music certainly did not depend on the lyrics.
Most pop singers, however, try to emote on purpose, with the effect that it loses its authenticity--one simply doesn't believe that they are feeling the emotion they seem to be expressing. Even if they are good singers (and usually they are not, at least not without Autotune), they are not good enough actors. Performers often don't actually feel what they are performing--doing so would often be distracting to them--but the good ones sustain the illusion that they do.
Rebecca Pidgeon put out an album skillfully recorded by Chesky a decade or two back. Her singing is nearly minimalist in its lack of decoration. She doesn't use much vibrato, nor does she modulate the dynamics a lot. What she adds, however, is a superb sense of timing and phrasing. She is an actress who sings, and is therefore trained to express emotion subtly to give the impression that we are seeing only the tip of the emotion iceberg. The result is that of strong emotion felt but restrained rather than exaggerated, which makes the emotion stronger in my ears. I recall from my youth an acting teacher (the teacher was Jeanette Clift, and I was not a student, but was on-hand when she gave this advice to one of her students)--if a scene calls for crying, instead of crying, try hard NOT to cry, and the audience will do the crying for you.
Someone mentioned Aretha Franklin whose more overt musical decoration consistently supported the illusion of felt emotion. That authenticity is the reason she is legendary. And Barbra Streisand who--no surprise--turned out to also have real acting chops.
Rick "vibrato is not an emotion" Denney