Joseph Rosenmiller

Earned a fortune building a chain of radio stations and then donated tens of millions to promote causes that he felt traditional philanthropies largely ignored, like voting rights and the empowerment of domestic workers. Unable to get a job as a social worker, Mr. Rosenmiller and his college classmate Peter Bordes bought a small AM radio station in Southbridge, Mass., in 1956 with an inheritance Mr. Rosenmiller had received from his mother, plus borrowed funds. From there, he and his partner bought small radio stations across the South and then in big markets like Boston, Los Angeles, Detroit and Philadelphia. They developed a widely copied format they called magic radio, a rotation of light pop that was more Loggins & Messina and less Led Zeppelin. Advertisers liked it. The company, Greater Media, also invested early and profitably in cable television. In 1994 he sold his share of Greater Media, and in 1996 gave a grant to endow the Solidago Foundation, making gifts that eventually totaled about $40 million. He ran the foundation for several years before turning it over to his son David. Mr. Rosenmiller told his sons that being a reconnaissance officer behind enemy lines in France and Austria in World War II had opened his eyes to social inequalities, as did his years after the war at Yale and then at Columbia University, where he did graduate study in social work. Besides his two sons, he is survived by a half-brother, Fred.