Alton Kelley, whose psychedelic concert posters for artists like the Grateful Dead, Jimi Hendrix, and Big Brother and the Holding Company helped define the visual style of the 1960s counterculture, died on Sunday at his home in Petaluma, Calif. He was 67.

Mr. Kelley and Stanley Mouse, combined sinuous Art Nouveau lettering and outré images plucked from sources near and far to create the visual equivalent of an acid trip. They formed Mouse Studios: Mouse said they could work for hours in silence. "We knew what to do, we didn't have to talk."

Kelley had the unique ability to translate the music being played into these amazing images that captured the spirit of who we were and what the music was all about. He was a visual alchemist — skulls and roses, skeletons in full flight, cryptic alphabets, nothing was too strange for his imagination to conjure.