Joseph Mascolo, who played the crime boss Stefano DiMera on the NBC soap opera “Days of Our Lives” across three decades, last appearing on the show this year, died on Dec. 8 in Santa Clarita, Calif. He was 87.

The cause was Alzheimer’s disease, his wife, Patricia Schultz-Mascolo, said.

Mr. Mascolo was a classically trained musician and appeared on Broadway in “Dinner at Eight” and “That Championship Season,” among other productions.

His TV credits included the prime-time series “Kojak,” “Hill Street Blues” and “It’s Garry Shandling’s Show.”

His long run as the mob boss on “Days of Our Lives” began in 1982, though he took breaks from the show over the years. His last appearance was in July.