The cause was complications of a stroke he had suffered three years ago, said Kurt Vitolo, his business manager.

As Mr. Masser biked to work as a broker in Midtown Manhattan in the 1960s, he would detour to the Juilliard School to putter on a piano. A self-taught pianist, he could not read music, but an inner muse was urging him to switch careers (he had earlier dropped out of law school) and pursue his true calling.

“I was working as a stockbroker in New York and had the seemingly perfect life,” Mr. Masser told The Chicago Sun-Times in 1988. That life included an office atop the Pan Am Building, a nine-room apartment and a farm in Vermont. “But I was unhappy, and someone I knew convinced me to see a shrink. I walked in and told the doctor I wanted to write music.

He said, ‘What’s the problem with that?’

I told him that didn’t go over well in my family. He listened, took my money and said: ‘Here’s a note of permission to write music. That’s all you need to clear your conscience.’

“And it’s funny, because that’s all I was looking for: permission,” he continued. “I had been the dutiful son and husband for so long, I had forgotten about living for myself.”

With the celebrated songwriter Johnny Mercer as a mentor — Mr. Mercer tutored him at his Hollywood guesthouse in the early ’70s — Mr. Masser began composing ballads with epic sweep. Many of them reached the top of the charts.

In 1973, he wrote (with the lyricist Ron Miller) and produced “Touch Me in the Morning.” Released as a single by Motown, it revitalized Diana Ross’s career and started his own. It hit No. 1 on the Billboard singles chart and remained on the list for 21 weeks.

His “Theme From ‘Mahogany’ (Do You Know Where You’re Going To?),” with lyrics by Gerry Goffin, recorded by Ms. Ross and featured in a 1975 film in which she starred, was nominated for an Academy Award for best original song and reached No. 1 on the singles chart. Ms. Ross also sang (and had a Top 10 hit with) his “It’s My Turn,” with lyrics by Carole Bayer Sager. The theme from the 1980 film of that name, it was praised in a New York Times review by Janet Maslin as a “hugely effective theme song.”

While producing Teddy Pendergrass’s 1984 album “Love Language,” Mr. Masser met Whitney Houston, who sang a duet with Mr. Pendergrass on “Hold Me,” which Mr. Masser had written with Linda Creed. Shortly thereafter he began a collaboration with Ms. Houston, as both composer and producer, that catapulted her to stardom. Among the chart-topping singles by Ms. Houston he wrote were “The Greatest Love of All” (with Ms. Creed), “Saving All My Love” (with Mr. Goffin) and “Didn’t We Almost Have It All” (with Will Jennings).

His other hits as a songwriter included “Tonight, I Celebrate My Love,” with Mr. Goffin, a Top 20 single for Peabo Bryson and Roberta Flack in 1983; “Nothing’s Gonna Change My Love for You,” also with Mr. Goffin, a Top 20 hit for Glenn Medeiros in 1987; and “Miss You Like Crazy,” with Mr. Goffin and Preston Glass, a Top 10 single for Natalie Cole in 1989. In 2007, Mr. Masser entered the Songwriters Hall of Fame.

He graduated from the University of Illinois and enrolled in its law school, but left to work as a theatrical agent and stockbroker in New York.

“I come from a background that stresses education more than anything,” Mr. Masser told The Sun-Times. “You get your hands cut off if you don’t get a law degree or become a doctor. I was used to being successful in school, but academics didn’t make me happy.”

His first marriage ended in divorce. He is survived by his wife, the former Ogniana Drandiyska; two daughters, Jennifer Convery and Aleksandra Rouschkolb; a son, Sean Masser; two grandsons; and a sister, Rhoda Lev.

Mr. Masser was a perfectionist, cajoling Ms. Houston into singing one verse at a time over and over, just as Berry Gordy of Motown had persuaded him to mix 79 versions of “Touch Me in the Morning” until it was flawless.

“The biggest thing I got from Johnny was, ‘Don’t rush a song,’ ” Mr. Masser recalled of Mr. Mercer to The Desert Sun of Southern California. “And the thing I ran up against was everybody wanted a song so fast. It took me two years to finish ‘Touch Me in the Morning.’ ”

Mr. Masser would spend months searching for the right sound, just as he had taken years to find a fulfilling career.

“Somehow people get very nervous about leaving the comfortable life of rules behind,” he told The Christian Science Monitor in 1989, “and never take the chance to develop their own internal voice, to listen to their own consciousness.”