KEITH Emerson, the co-founder of progressive rock group Emerson, Lake and Palmer, has died at the age of 71, with police investigating his death as a possible suicide.

Emerson was found dead by his long-time girlfriend at their Santa Monica, California, condominium, it emerged yesterday..

Police sergeant Erika Aklufi said Emerson had an apparent self-inflicted gunshot wound to the head.

Emerson, who was born in Yorkshire, drummer Carl Palmer and vocalist/guitarist Greg Lake were giants of progressive rock in the 1970s, recording six platinum-selling albums.

They and other hit groups such as Pink Floyd, the Moody Blues and Genesis stepped away from rock's emphasis on short songs with dance beats, instead creating albums with ornate pieces full of complicated rhythms, intricate chords and time signature changes.

Emerson had been composing and working with internationally known symphony orchestras and was about to embark on a short tour in Japan starting on April 14 with his band.