Mr. Harrison came up with the idea to substitute hemp — the industrial fiber from marijuana — for paper in the vibrating cone in speakers of guitar and bass amplifiers. R.E.M.’s Pete Buck said the “hempcone” speakers gave him “the coolest, most authentic early ’60s garage band tone.”

Mr. Harrison tried them out first on Santana, a longtime customer of his speaker repair shop.

“Santana was the first guy in the world to play through hemp and he immediately loved it,” Mr. Harrison said in a Marin Independent Journal article last year. “Eight years later he’s still using the originals.”