There are tons of Isolated Vocal tracks on Youtube. They can be hilarious like David Lee Roth's to super intense like Kurt Cobain. But this one I found on Open Culture is pretty amazing. Queen's "Under Pressure" was recorded in 1981, before the world went digital and way before Auto-Tune became the biggest scam in music. Check out Freddy Mercury killing it here.
And just for fun, here's Lemmy from Motorhead ripping through "Ace Of Spades". You can hear every cigarette, bottle of whiskey, and mile of bad road in that gravel pile of a voice. Auto-Tune would just ruin that.