Their songs were spun into hits by, among others, Aretha Franklin, Diana Ross, Gladys Knight, Marvin Gaye, Chaka Khan, Whitney Houston and Ashford & Simpson themselves – including the '80s hit "Solid As a Rock."
Ashford and Simpson's relationship went back to 1964, when they (she a 17-year-old from the Bronx, he a 21-year-old from Michigan) met in a Harlem church and decided to write songs together. They wed 10 years later.
"Being married is the best thing that ever happened to me," Ashford told PEOPLE in 1978. "I don't feel like I'm married. Valerie brought me around to the idea that every time you fight it isn't the end. You can knock each other down but then you make love."
They had their first hit in 1966, when Ray Charles recorded "Let's Go Get Stoned." Motown quickly signed them to write for Ross, Gaye and Tammi Terrell, and the relationship with that label lasted seven years. Simpson cut her two solo albums for Motown. But in 1973, said Ashford, "We felt it was time for growth, to reach out as artists."
The duo moved to the Warner Bros. label and also started producing albums for others, which they found less satisfying artistically but highly lucrative, allowing them to purchase a four-story Manhattan townhouse with a staff of five, and a 14-room Westport, Conn., estate with a pool, tennis courts and a barn that doubled as a stable for horses.
They were married in that Connecticut house after a long platonic spell and a couple of years of living together. Simpson admitted to PEOPLE that she was reluctant.
"First he decided we should have a baby," she said with a laugh. "Then we bought the house. I still thought getting married was, oh, so old. I wanted him to think of me as his woman, not his wife. But when I realized that I felt secure enough to allow him all the freedom he needed, we went ahead."
Besides Simpson, Ashford is survived by their two daughters, Nicole and Asia; his brothers Paul, Albert and Frank; and his mother, Alice Ashford.