Pee Wee Ellis, a saxophonist who was the musical director for soul star James Brown in the late 1960s and is considered an architect of funk music for his groundbreaking songwriting and arrangements on such songs as “Cold Sweat” and “Say It Loud — I’m Black and I’m Proud,” died Sept. 23 at age 80.

His official Facebook page announced his death, citing “heart complications.” No further details were available. He had lived in the southern English county of Dorset since the early 1990s.

Mr. Ellis began his career as a jazz saxophonist and had fronted rhythm-and-blues bands before he became part of Brown’s ensemble in 1965.

“Being a jazz-head, I really wasn’t that aware of James Brown when I joined the band,” Mr. Ellis told ABC News in 2015, “but my first night in the wings watching the show, which all new band members had to do, took my breath away. . . . I couldn’t believe what I was seeing.”

Brown had been renowned since the 1950s for his impassioned vocals, nonstop dancing and dramatically emotional performances, in which his backup musicians segued from one song to another without a break.

Mr. Ellis joined the horn section on alto saxophone before switching to the larger, deeper-toned tenor saxophone, his preferred instrument. He was also a capable organist. Within two years, he had become Brown’s musical director.

“A lot of stuff rubbed off on me about how to lead a band,” Mr. Ellis said of Brown. “He said, ‘If it feels good, do it. If it sounds good, don’t analyze it, just do it. It’s about the groove and the feeling.’ ”

Brown, who was always on the lookout for material, invited Mr. Ellis to help him write music for the group.

“We were in the Apollo Theater in Harlem,” Mr. Ellis said in a 2020 interview with the American, a magazine for U.S. expatriates in Britain. “Mr. Brown called me into his dressing room and said ‘I got an idea,’ and he started grunting, like ‘Uh. Uh-uh-uh. Uh.’ . . . We got on the bus, and in the back I had this setup where I could write music. I wrote what I considered were the ‘grunts,’ and kept it in my mind — that turned out to be the bass line of ‘Cold Sweat.’ I had been listening to Miles Davis, and ‘So What’ was in my mind too, and that gave me an idea for the horn line of ‘Cold Sweat.’ ”

The song was recorded in 1967, quickly became a No. 1 R&B hit and rose to No. 7 on the Billboard pop chart. With its propulsive, syncopated pulse, torrid horn solos and scratching rhythm guitars, “Cold Sweat” became recognized as one of the first songs in a new genre that came to known as funk.

During their four years together, Mr. Ellis and Brown collaborated on 26 songs, but none had a greater impact than “Say It Loud — I’m Black and I’m Proud,” which was recorded in 1968, months after the assassination of the Rev. Martin Luther King Jr. and during a summer of civil unrest and growing Black pride.

“I rehearsed the band through that song — getting the horn parts right and guiding the bass player through his lines — and the next day Mr. Brown showed up,” Mr. Ellis told England’s Independent newspaper last year. “He had the words he’d written on a napkin he’d kept in a brown paper bag. By the time we played it through a couple of times, we knew it was working.”

The song had an unforgettable opening line that could have been uttered only by Brown: “Uh! With your bad self!”

The lyrics were a powerful plea for justice and Black solidarity:

We’re people, we like the birds and the bees

We’d rather die on our feet

Than be living on our knees

Say it loud: I’m Black and I’m proud!

The song was No. 1 on the R&B chart for six weeks and reached the top 10 of Billboard’s Hot 100 pop chart. It was immediately adopted as an anthem by civil rights groups, and its repeated refrain, “Say it loud, I’m Black and I’m proud,” appeared on buttons, T-shirts, coffee mugs and protest signs.

The song’s message and dynamism remained undiminished more than 50 years after it was released. In 2020, it re-emerged as a rallying cry for the Black Lives Matter movement in the wake of the murder of George Floyd by a Minneapolis police officer.

“I’m deeply proud,” Mr. Ellis said last year, “to have played a part in creating a song that is inspiring young people today.”

Alfred James Rogers was born April 21, 1941, in Bradenton, Fla. When his mother remarried a few years later, he took his stepfather’s last name and moved with the family to Lubbock, Tex. He acquired the nickname Pee Wee as a child.

His stepfather, a cook and music promoter, was stabbed to death at a Lubbock dance hall in 1955, ostensibly for dancing too close to a White woman. Mr. Ellis said the closest hospital would not treat his wounds because he was Black.

“He was left to die on a gurney in a hallway,” Mr. Ellis told the Independent last year.

He then moved with his mother and two sisters to Rochester, N.Y. In his teens, Mr. Ellis was drawn to jazz, often playing saxophone alongside future trumpet star Chuck Mangione and jazz bassist Ron Carter, who later became a mainstay of the Miles Davis Quintet.

While in New York to have his instrument repaired in 1957, Mr. Ellis told the Rochester Democrat & Chronicle in 2011, “I saw a guy walking toward me with a saxophone. It turned out to be Sonny Rollins,” a major jazz star. Mr. Ellis asked whether he could take lessons, and, much to his surprise, Rollins agreed.

“I guess he saw the desperation in my eyes and the sincerity,” Mr. Ellis said. He flew to New York every week to meet Rollins. He also studied at the Manhattan School of Music before moving to Florida, where Brown saw him leading a group at a club.

“The reason I decided to join James Brown’s band is I wanted to be able to afford to play jazz,” Mr. Ellis said.

He left Brown’s group in 1969. An instrumental tune he wrote that year, “The Chicken,” became a favorite of jazz fusion musicians and was popularized by electric bassist Jaco Pastorius.

During the 1970s, Mr. Ellis founded a jazz-funk band called Gotham and helped produce albums for George Benson, Hank Crawford and Esther Phillips, among others. He later moved to Northern California, where he formed a group with saxophonist Dave Liebman.

In 1979, British rock star Van Morrison invited Mr. Ellis to help with musical arrangements for his album “Into the Music.” Mr. Ellis was Morrison’s musical director for six years, then for four more years in the 1990s.

His first marriage, to Barbara Tringali, ended in divorce. Their son, Albert Ellis Jr., died in 2019. Survivors include his wife since 1994, Charlotte Crofton-Sleigh.

Beginning in the 1980s, Mr. Ellis reunited with two former Brown bandmates, alto saxophonist Maceo Parker and trombonist Fred Wesley and toured as the “JB Horns.”

“Your general layman may not know it, but it’s difficult to put into words how important and meaningful they have been to every generation of musicians that has followed them,” jazz bassist Christian McBride told the New York Times in 2011. “Any time you hear a remotely funky horn section, you know you are listening to something that comes directly from the legacy of Maceo, Fred and Pee Wee, with James Brown.”

From 2008 to 2011, Mr. Ellis organized “Still Black, Still Proud: An African Tribute to James Brown,” a touring group of American and African musicians. He continued to perform in British clubs and festivals until weeks before his death.

“We had so much fun,” Mr. Ellis said of his years with Brown, “we were almost ashamed to take money for it. But I got over it!”