Fornatale died in New York a week after suffering a stroke, his son, Peter Thomas Fornatale, told The Associated Press.
"He represented the golden age of progressive FM radio," he said.
When The Beach Boys "were the most uncool thing in the world," he said, his father had the clout, in the 1970s, to help make them popular again - by introducing them on the Carnegie Hall stage.
Fornatale entered with a surfboard.
"It's a very sad day for radio," said songwriter Paul Simon. "New York has lost one of its most acclaimed and wonderful radio personalities. ... He really knew his era and his music."
At New York's Fordham University, the DJ's alma mater, president Joseph McShane called Fornatale "the voice of several generations" who conducted soul-searching interviews with the hottest musicians and played their work.
As a DJ on WNEW-FM in the 1970s, he established a loyal following by spinning records by lesser-known artists and album cuts beyond the hit singles.
One of his favorites was Poco, a country-rock band he championed.
He helped launch the careers of singer-songwriters like Suzanne Vega, John Gorka and Christine Lavin. Grammy winner Shawn Colvin told The New York Times in 2001, "Pete helped pave the way for so many of us. He was a rare guy in radio then."
In the 1990s, Fornatale was featured on the station known as "K-Rock," following Howard Stern's show.
Fornatale's hallmark was "to use music in a very creative way," his son said.
"He could take a song that you heard a hundred times, but play it in a context - whether on a special occasion or the music around it - that would make some of the most familiar tracks in rock history sound like you were hearing them for the first time."
Until his death, his father still hosted the show "Mixed Bag" on Saturdays for Fordham University's WFUV-FM station.
The Bronx native was a Fordham student DJ when he developed the style that grew into the kind of FM rock broadcasting listeners still enjoy.
"The complete freedom to put this package together, for better or for worse stamped me then and is still with me today," Fornatale said in 2001.
In recent years, he also became a rock historian.
He and his son worked together on a book celebrating the Rolling Stones' 50th anniversary that they finished just before Fornatale's death, titled "50 Licks," to be published later this year or in early 2013. The DJ also wrote "Bookends," the story of the Simon & Garfunkel album by that title.
Fornatale leaves three sons, including Mark and Steven, and his former wife, Susan Fornatale, all of New York.
The funeral will be private, but a tribute concert is planned for a date to be set.