LOS ANGELES — Keith Emerson, founder and keyboardist of the progressive-rock band Emerson, Lake and Palmer, has died. He was 71. Emerson’s longtime partner, Mari Kawaguchi, called police to his condominium in Santa Monica, California, at about 1:30 a.m. on Friday. Emerson had an apparent self-inflicted gunshot wound to the head, and authorities are investigating his death as a possible suicide.