This cannot be underlined and stressed enough. Chester even reiterated this fact in Carpool Karaoke. He was not always a 'screamer', and a lot of his earlier works with Grey Daze and Sean Dowdell and His Friends? contained aggressively sung vocals (at best) and none of the kind of screams you hear on songs like Given Up, Faint, One Step Closer etc. He didn't even explore that side of his voice until he joined the band. So yeah, while he became known by some for having a powerful screaming voice, he was a full on singer before Linkin Park.