Question: Twista Screw Voice

Whut up,
I'm sure you guys heard the twista album, he has a song name heart beat, I think, but he did something to he voice to make it different, much deeper to make it sound like 2 people, for those that have heard it, how did he do it

copy vocal, pitch shift down, modulate it a lil bit if you're feelin frisky

thanks I'll try