That's ... kind of weird, right? For comparison (we're so sorry), you should have a few listens to Donny Osmond. Donny was about Michael's age and enjoyed a similar career for a while there. Here's Donny singing with an admirable little baby voice in 1972. Notice what happens, though, two years later when he banters with MJ at the 1974 Oscars.
It's like listening to a mouse and Barry White try to carry on a conversation. A few years later, while Michael was putting together his world-changing Off the Wall album, Donny was serenading Miss Universe contestants with his man-voice. (Once again, we're sorry.)
Donny's career also suffered from constant attacks by ivory poachers.
So what's the deal?
Well, one professor of vascular surgery thinks that Michael's consistently high voice was the key to understanding everything about his adult career. (No word if it explains the spangly military uniform phase, though.)
It was all due to some medication he took.
The kind that's been known to grow boobs on male patients.