Roger Williams, 87, a pianist who was one of the most popular instrumentalists of the mid-20th century and who hit No. 1 on the pop charts in 1955 with “Autumn Leaves,” died Oct. 8 at his home in Los Angeles.

He had complications from pancreatic cancer, his former publicist, Rob Wilcox, told the Associated Press.

Mr. Williams was the rare instrumental pop artist to strike a lasting commercial chord. Between 1955 and 1972, he had 22 hit singles — including “Born Free” in 1966 — and 38 hit albums, according to the AllMusic Internet database.

Mr. Williams played for nine presidents, beginning with Harry S. Truman. His last performance at the White House was in 2008.

“The biggest thing I have to offer is emotion,” Mr. Williams told Time magazine in 1968, “I think I play with more feeling than any other pop pianist.”

“Autumn Leaves” was the most successful song of Mr. Williams’s career and the first No. 1 instrumental song on the Billboard charts of the rock era, according to “The Billboard Book of Number 1 Hits.”

After Mr. Williams was signed to Kapp Records in the early 1950s, label president Dave Kapp asked him on a Friday if he would record “Autumn Leaves” the following Monday.

“I said, ‘You mean ‘Falling Leaves’? I didn’t even know the title,” Mr. Williams told the Los Angeles Times in 1996. “I stayed up Friday and then Saturday night working on an arrangement.”

“The first thing that came to mind was to play all those runs down the keyboard,” Mr. Williams said in an earlier Times interview. “I tried to make it sound like falling leaves.”

The first recording run-through was slightly more than three minutes, so Kapp asked him to speed it up because DJs at the time wouldn’t play a song longer than that length, Mr. Williams often said.

The second time around, “Autumn Leaves” came in at 2:59.

“I owed two months’ rent on our apartment,” Mr. Williams said in the 1996 interview. “I had a wife and a baby at the time. My fondest dream for ‘Autumn Leaves’ was that it would pay the rent. And boy, it’s been doing it ever since.”

The tunes he played were so familiar “they almost play themselves,” the New York Times wrote in a 1972 review of a performance that included “On a Clear Day,” “Hello, Dolly” and “The Impossible Dream (The Quest).”

If dissected, Mr. Williams’s approach could seem “trite and oversimplified,” the review said. “There is a cumulative charm to the unadorned simplicity and sincerity of his performance that can eventually win over even the most cynical listener.”

The son of a Lutheran minister, Mr. Williams was born Louis Weertz on Oct. 1, 1924, in Omaha. He grew up in Des Moines.

He often recalled that, at age 3, he toddled toward the piano and just began playing.

While majoring in piano at Drake University in Des Moines, he began developing a style that was a fusion of jazz, classical and pop.

When a school official overheard him playing the tune “Smoke Gets in Your Eyes,” he was expelled because the school had a “classics-only” policy, Mr. Williams later said.

He joined the Navy during World War II. He developed an aptitude for engineering and earned a bachelor’s degree in the subject in 1949 at Idaho State University. The next year, he earned a master’s degree in music.

While enrolled at the Juilliard School in New York, he won “Arthur Godfrey’s Talent Scouts” on television by playing a symphonic arrangement of “I Got Rhythm.”

Kapp insisted that the pianist “have a name that would stand up anywhere” and changed it to Roger Williams, after the founder of Rhode Island.

Mr. Williams’s top 10 albums include “Songs of the Fabulous Fifties” (1957), “Till” (1958), “Maria” (1962) and “Born Free” (1966).

In the early 1970s, his popularity faded but he went on to record more than 100 albums and performed in concert as recently as March.

— From news services