It wasn't a vocal technique. It was pain.
A detailed breakdown of a (like Thriller or Bad ). multitrack michael jackson
Look into the used by his audio team
In recording studio terms, a "multitrack" is the original collection of separate audio sources that make up a song. Instead of hearing the final blended version, multitracks allow you to isolate individual elements: MJ’s raw performance before layering. It wasn't a vocal technique
Compare Jackson's multitrack techniques with recording methods. multitrack michael jackson