He also found some success in the '80s and '90s as a film and TV composer.
According to ELP's official Facebook page, Keith passed away in his Santa Monica home Thursday night. Drummer Carl Palmer said in a statement:
"I am deeply saddened to learn of the passing of my good friend and brother-in-music, Keith Emerson. Keith was a gentle soul whose love for music and passion for his performance as a keyboard player will remain unmatched for many years to come. He was a pioneer and an innovator whose musical genius touched all of us in the worlds of rock, classical and jazz. I will always remember his warm smile, good sense of humor, compelling showmanship, and dedication to his musical craft. I am very lucky to have known him and to have made the music we did, together. Rest in peace, Keith."
Our thoughts are with Keith's family, friends, and fans.
See Keith rocking the keys like no one else in this throwback clip (below):