Joseph Brooks, 73, was found on his living room couch with a plastic dry-cleaning bag around his head and a towel around his neck, police spokesman Paul Browne said.
Brooks left a three-page suicide note that complained of his health, but a coroner will determine the exact cause of death, investigators said.
Brooks, who wrote the song "You Light Up My Life," is accused of luring more than a dozen women to his apartment and then sexually assaulting them. Officials said Brooks lured the women by offering auditions for a movie role though an online ad. He pleaded not guilty in 2009, and his court date had not yet been set.
The songwriter's son, Nicholas Brooks, is charged with murder in the death of his girlfriend, Peruvian-American swimsuit designer Sylvie Cachay.
The 24-year-old has pleaded not guilty and is being held without bail at the Rikers Island jail complex.
The Associated Press contributed to this report.