This is a topic I love and analyze frequently, as I enjoy creating recreations. The work allowed me to differentiate the color of MJ's voice in each era; he had a special way of singing. In each decade, you saw an "evolution," or an attempt to add something new.
I particularly love his voice in the late 2000s; it reminds me of the softness of the voice he used in his youth, when he didn't want to stray from "what the public knew" with the Jackson 5. I see that sweetness and smoothness present until the late 1970s and occasionally in some performances until 1984.
Attempting to make his voice harder and heavier from the Bad era to HIStory seems to have had consequences. Although it's said he had more vocal range, to my ears, the "raspy" was never entirely to my liking. I like the high, clear notes he hits in shows like the one in London in '79.
Something I think he was trying to recover in the 2009s. Or maybe he used it as a resource, as he himself mentions in "This Is It," "to take care of" his voice.
But even in IJCSLY (pitch correction aside), he sings with a softness that's different from the original, not to mention what we heard live back in time in tours