In 1976, Judas Priest recorded Sad Wings Of Destiny with Rob Halford on lead vocals and at 7:19 into the song Victim Of Changes, Halford begins what may be the first false fold scream on record.
Halford absolutely does a false fold scream from about 7:19 to seven twenty two and a half seconds and you might argue that from about seven twenty two and a half seconds on, that maybe it no longer is a false fold scream and you'd be right. It's something much harder to do.
At somewhere between 7:22 and 7:23, Halford's false fold scream transitions into something where the sound from the true vocal folds can be much more clearly heard despite a massive amount of distortion over his voice. Essentially from seven twenty two and a half seconds on, the false fold scream becomes a "distortion siren" that peaks at A5!
It's a remarkable achievement for any vocalist, but by 1976 standards, this was the metal equivalent of what putting a man on the moon was in 1969.
Here's the link