His publicist, Joe Gordon, announced the death, saying the singer had been treated for exhaustion. The cause was not immediately known.
Mr. Jarreau was loosely classified as a jazz singer, but his eclectic style was entirely his own, polished through years of obscure apprenticeship in lonely nightclubs. He did not release his first album until 1975, when he was 35, but within two years, he had won the first of his seven Grammy Awards and had begun to attract a wide following.
He was dubbed the “acrobat of scat” for the way he adopted the fast, wordless syllables of bebop jazz musicians, but he did not limit himself to the musical backdrop of an earlier generation. His approach emphasized the percussion-heavy and electronically amplified sound of rhythm-and-blues and funk music, and he had a particular gift for mimicking almost any kind of musical instrument or sound.
“Jarreau imitates the electronic and percussive hardware of the 1970s,” critic Robert Palmer wrote in Rolling Stone in 1979. “But he does more than that. He stands there and makes it all sound natural, singing so sweetly and unaffectedly you’d think he just happened on this remarkable vocal vocabulary.”
After winning awards and plaudits as a jazz singer, Mr. Jarreau found a wider audience with his 1981 album “Breakin’ Away,” which sold more than 1 million copies and included a Top 20 hit, “We’re in This Love Together.” The album won Grammy Awards in the jazz and pop vocal categories, propelling Mr. Jarreau to widespread stardom.
He was soon appearing on television, touring with a 10-piece band and taking the stage with dramatic lighting and choreographed dance moves. He seemed poised for a popular breakthrough that never quite arrived. Despite his Grammy Awards and growing acclaim, Mr. Jarreau groused that Lionel Richie, Stevie Wonder and Al Green sold more records, even though they — in the view of many, including Mr. Jarreau — could not match his vocal chops.
As the 1980s wore on, Mr. Jarreau explored rock, reggae and international music and recorded the theme song for the TV series “Moonlighting.” His 1992 album “Heaven and Earth” won a Grammy for best R&B vocal performance, giving Mr. Jarreau Grammys in three categories.
He branched out into other fields, performing with symphony orchestras and acting on Broadway in 1996 in the role of Teen Angel in “Grease.”
As time went on, Mr. Jarreau returned to his early inspiration in straight-ahead jazz. He recorded an album of jazz standards in 2004 called “Accentuate the Positive,” which included songs by Dizzy Gillespie, Duke Ellington and Johnny Mercer and was considered a triumphant return to form.
“It’s really the first jazz record I’ve ever done,” Mr. Jarreau told Billboard magazine. “Everything else that came before was pop and R&B. This is a thanks to the kind of music that made me the person I am today.”
Alwyn Lopez Jarreau was born March 12, 1940, in Milwaukee. His father, originally from New Orleans, was a former Seventh-day Adventist preacher, and his mother was a piano teacher. Mr. Jarreau sang gospel in church and doo-wop on street corners, absorbing the many musical styles of his melting-pot home town.
He had listened from an early age to Nat King Cole, Billy Eckstine, Sarah Vaughan and Ella Fitzgerald, but his two greatest influences were jazz scat artist Jon Hendricks and the smooth ballad singer Johnny Mathis.
“A lot of who I am is described in the qualities of those two guys — the fiery jazz singer and the balladeer — and how they performed,” he said in 2005. “Somewhere in there, too, is an R&B guy who went to Motown University.”
An excellent athlete, Mr. Jarreau tried out with the Milwaukee Braves baseball team and played basketball at Wisconsin’s Ripon College, from which he graduated in 1962. He sang in dance bands in college and graduate school and, in 1964, received a master’s degree in vocational rehabilitation from the University of Iowa.
After moving to San Francisco, Mr. Jarreau worked by day as a counselor for the disabled and sang in jazz clubs at night, quitting his counseling job in 1968 to devote himself to music. Working with a Brazilian guitarist, he learned to fill empty musical spaces with expressive improvisations. He devised inventive versions of songs by Joni Mitchell and the Beatles, wrote original tunes and seemed at home in any musical style.
In 2007, he won two more Grammys for a recording made with guitarist George Benson, “Givin’ It Up.” Mr. Jarreau remained in demand in recording studios and on concert stages around the world into his 70s. He received a star on the Hollywood Walk of Fame in 2001, hosted a public television program on jazz singing and established a scholarship fund at the University of Wisconsin at Milwaukee for students interested in becoming teachers.
His marriage to Phyllis Hall ended in divorce.
Survivors include his wife of 39 years, Susan Player, and a son from his second marriage.
Never one to stay in one physical or musical place for long, Mr. Jarreau described his constantly evolving approach to music to the Chicago Tribune in 1989.
“Jazz, whatever we think its purest form is, is a dynamic and changing form,” he said. “It will never be the jazz of the 1930s and ’40s and ’50s, because it’s changing and responding to its environment. That environment includes the influences of Michael Jackson, Sting and hip-hop just as much as Charlie Parker or bebop.”