Eddie Harris Scream

Hey everyone, it's been a while since I've SOTWed, but that's what happens when you're a college junior...

Anyways, I saw this video and I couldn't help but beat myself up over how the heck he does that scream every now and then. I'd think it's some altissimo multiphonic, but do those even exist? I'd love to know how to do that since my style of playing is very much like that these days and that's such a crowd pleaser.

And yes, that's the First Lady of Jazz walking in in the middle of the clip.

Thanks for any info!

And here's the video: