The band he led with his brother broke new ground with an unusually broad repertoire, unorthodox instrumentation and untraditional vocal harmonies.
Bobby Osborne, the singer and mandolin player who with his younger brother, Sonny, led one of the most groundbreaking bands in the history of bluegrass, died on Tuesday at a hospital in Gallatin, Tenn., a suburb of Nashville. He was 91.
His death was confirmed by Dan Rogers, the vice president and executive producer of the Grand Ole Opry.
Formed in 1953, the Osborne Brothers band habitually flouted bluegrass convention during its first two decades. They were the first bluegrass group of national renown to incorporate drums, electric bass, pedal steel guitar and even, on records, string sections. They were also the first to record with twin banjos, as well as the first to amplify their instruments with electric pickups.
Employing a wider repertoire than the Appalachian wellspring from which most of their peers drew, the Osbornes also worked with a more expansive musical palette, embracing country, pop and rock material associated with the likes of Ernest Tubb, Randy Newman and the Everly Brothers.
“We caught lots of flack from the die-hard bluegrass fans,” Mr. Osborne said of the group’s sometimes fraught relationship with bluegrass purists in a 2011 interview with the online publication Mandolin Café.
Perhaps nothing the Osbornes did rankled the bluegrass orthodoxy more than the three-part vocal harmonies they patented on their 1958 recording of the lovelorn ballad “Once More.”
At the time, bluegrass arrangements typically featured one voice singing the melody, with a tenor and a baritone supplying harmonies above and below it. By contrast, the Osbornes positioned Bobby’s voice, singing the melody, above the two other voices. The result was the bright, euphonious blend that became the group’s trademark.
Mr. Osborne told NPR in 2017 that the group discovered this sound while rehearsing “Once More” as they drove home from a show one night. “We knew then,” he said, “that we caught onto something that we had never heard before.”
“So we got the guitar out of the trunk and found out what key we was in,” he continued. “We sang that song all the way home so we would not forget that type of harmony.”
The trio that perfected this new approach consisted of Mr. Osborne, his bold high-pitched lead the focal point; his brother, Sonny, on baritone; and the singer and guitarist Red Allen on another part beneath them both, adding a third layer of harmony.
A formative member during the group’s early years, Mr. Allen had previously appeared on the Osbornes’ popular 1956 recording of “Ruby, Are You Mad?,” an unbridled two-banjo romp written by the old-time country singer Cousin Emmy, a.k.a. Cynthia May Carver.
To the surprise of some people, the Osbornes were vindicated over the next decade and a half for steadfastly breaking with tradition. Among other accomplishments, they were named vocal group of the year by the Country Music Association in 1971. They were also one of the few bluegrass bands to consistently place records on the country singles chart.
Along the way they built a bridge between first-generation bluegrass royalty like Bill Monroe and the duo of Lester Flatt and Earl Scruggs and intrepid latter-day inheritors like New Grass Revival and Alison Krauss.
Maybe the best known of the Osbornes’ 18 charting singles was “Rocky Top,” an unabashed celebration of mountain culture that reached the country Top 40 in 1967. Written by the husband-and-wife team of Felice and Boudleaux Bryant, who also wrote hits like “Tennessee Hound Dog” for the Osbornes — and even bigger hits for the Everly Brothers — “Rocky Top” was adopted as one of Tennessee’s official state songs and as the fight song of the University of Tennessee football team, the Volunteers.
Robert Van Osborne Jr. was born on Dec. 7, 1931, in Thousandsticks, an unincorporated Appalachian enclave near Hyden, Ky., where he and his brother grew up. Their parents, Robert and Daisy (Dixon) Osborne, were schoolteachers; Robert Sr. supplemented their teaching income by moonlighting in his parents’ general store.
Young Bobby took up the electric guitar as a teenager after the family moved to Dayton, Ohio, where he also began playing in local country bands and working as a cabdriver.
The Osborne brothers started their own band after Bobby completed two years of service with the Marines in Korea, where he was wounded in combat and earned the Purple Heart. He and Sonny had previously worked for bluegrass luminaries — Bobby with Jimmy Martin and the Stanley Brothers, his brother with Bill Monroe.
In 1956 the Osbornes joined the WWVA Jamboree in Wheeling, W.Va. Four years later they became one of the first bluegrass bands to perform on a college campus, appearing at Antioch College in Yellow Springs, Ohio. They subsequently took their music to universities and clubs in the Northeast and performed at the Newport Folk Festival.
In 1963 the brothers signed with the Nashville division of Decca Records, then run by the pre-eminent music producer Owen Bradley. In 1964 they became members of the cast of the Grand Ole Opry.
The Osbornes recorded extensively for Decca (which later became MCA Records) before they parted with the label in 1974, disillusioned that their initial success at country radio did not extend into the 1970s.
A return to a more time-honored approach to bluegrass revitalized their career, which over the next 30 years found them consolidating their place alongside pioneers of the genre like Mr. Monroe and the Stanleys. They were inducted into the International Bluegrass Music Association’s Hall of Fame in 1994.
Sonny Osborne retired from performing in 2005, after suffering a shoulder injury, and died in 2021. Bobby, who had previously undergone quintuple bypass heart surgery, formed a new group, Rocky Top X-Press, with his son, Bobby Jr. (known as Boj), and continued to perform and record.
Besides Bobby Jr., Mr. Osborne is survived by his wife, Karen Osborne; two other sons, Wynn and Robby; a daughter, Tina Osborne; a sister, Louise Williams; five grandchildren; and six great-grandchildren. He lived in Portland, Tenn., another suburb of Nashville.
Much has been made of the innovations in production, arrangements and repertoire that the Osbornes introduced to bluegrass. Less, however, has been said of how Mr. Osborne, whose syncopated, lyrical playing was inspired by the jazz-derived solos of old-time fiddlers, broke new ground as a mandolinist.
Speaking to the website Bluegrass Situation in 2017, he explained: “Since I always liked fiddle tunes and the mandolin is tuned like a fiddle — and I was good with a flat pick from guitar — I got completely wrapped up playing fiddle tunes with the mandolin.”
In the process Mr. Osborne earned a reputation as one of the first bluegrass mandolin players to expand the instrument’s vocabulary beyond what Mr. Monroe, the father of Bluegrass, had established early on.
Alex Traub contributed reporting.
