The dinner bell rings promptly at 4:15 p.m. for the Sons of the Pioneers Chuckwagon Show at the Shepherd of the Hills Homestead in Branson, Mo. The 300-seat pavilion is not quite half-full this weekday night in May. Kids are still in school, and the steady stream of tour buses that deliver many of Branson’s 7.8 million annual visitors to “the live music capital of the world” is only a trickle this early in the season. The friendly servers distribute heaping plates of beef brisket, chicken, and fixin’s among the long rows of checkered tablecloth-covered tables. About the time they make another round to hand out toothpicks and refill drinks, the Sons of the Pioneers take the stage against a Western-styled backdrop. The group launches into the opening strains of “Tumbling Tumbleweeds” by way of introduction, and an appreciative audience murmur of recognition swells to applause.

“We’re the Sons of the Pioneers and we’re thrilled to death to have ya’,” says lead singer and guitarist Randy Rudd shortly into the show. “We’re going to sing you lots of cowboy songs today and songs of Americana and some songs of historical significance.”

Over the next two hours—and as is the case May through October at least six nights a week—the Sons of the Pioneers do just that with their signature mix of harmony, humor, and a rich song catalogue that includes standards such as “Cool Water” and “Tumbling Tumbleweeds.”

The Sons of the Pioneers celebrated their 75th anniversary in 2009 and are reputed to be the longest continuously performing musical act in American history. The Smithsonian Institution has declared the group a national treasure, and they’ve been inducted into just about every music Hall of Fame there is, including the Country Music Hall of Fame, the Western Music Association Hall of Fame, and the National Cowboy and Western Heritage Museum’s Hall of Great Western Performers.

To say that their legacy looms large in popular music is an understatement. Regarded as the quintessential cowboy singing group, the unique harmony arrangements that originated with the Pioneers have been a blueprint for generations of musicians in Western music and beyond. The Eagles, the Osmond Brothers, the Lennon Sisters—even Elvis—have all paid tribute to the Pioneers.

Although such awards and adulation usually mark the twilight of a career, the most current incarnation of the Sons of the Pioneers (there have been 26 members, total) shows no signs of slowing. They are wholly devoted to keeping the legacy alive, because nothing less than the future of Western music is at stake.

Mention the Sons of the Pioneers to folks of a certain age, and they’ll wax nostalgic about going downtown to the local movie theater to see Roy Rogers, Dale Evans, Trigger, Gabby Hayes, and the Sons of the Pioneers in one of their classic Westerns like Song of Arizona. Mention the Pioneers to the children of those folks, and they’ll talk about growing up listening to old Pioneers albums and how every other show on television was a Western, including Maverick, for which the Pioneers recorded the theme music. Mention the Pioneers to their grandchildren and … blank stare.

“So much time has passed that a lot of younger people don’t know who Roy Rogers or the Sons of the Pioneers are,” says Luther Nallie, the group’s “trail boss”, who has performed with the Pioneers for a total of 42 years. “It’s been so long since they’ve been out on the forefront, and people will forget you quick.”

“I usually ask them if they’ve seen the Big Lebowski,” says bass player Mark Abbott, referring to the popular 1998 film that prominently features “Tumbling Tumbleweeds” during the opening scene.

While the Sons of the Pioneers may not be a household name anymore, their songs still influence popular culture, even if listeners can’t always place the name. However many children still do grow up listening to old Pioneers albums, especially in the West. Some of them, like Jack Hannah, have gone on to form musical groups of their own.

“No one held our respect and admiration like the Sons of the Pioneers,” says Hannah, 76, singer and songwriter with the Sons of the San Joaquin. “It seemed like we went to church seven nights a week growing up, and when we weren’t singing hymns, we’d sing the songs of the Pioneers.”

Ranger Doug—of Riders in the Sky, whose band took its name from the Pioneers album Riders in the Sky and shared billing with the group at the Grand Ole Opry last year—shares a similar story.

“‘Cool Water’ is the first song I can remember sitting down in front of the radio and hearing. It’s been a thread ever since my childhood,” says Doug. “The Pioneers are what inspired me to get together with Too Slim and try to work out those harmonies. We started out idolizing them and the music they produced in the classic years, and also the groups they directly influenced like Riders of the Purple Sage and Andy Parker. The new group sounds great and it’s an unbroken tradition.”

World Champion fiddle player Ricky Boen, who joined the Pioneers in 2006, also grew up listening to the band’s music. He’s acutely aware of his responsibility.

“Every Western group uses the Sons of the Pioneers songbook as the bible for Western music,” he says. “It keeps me on my toes when we’re on stage, because it’s a living legacy that we’re upholding. Everyone that’s come through the group all these years has left their mark in some form.”

The origins of the Pioneers date to the early 1930s. Western music was very popular during the Depression, especially on the West coast. Tim Spencer and Leonard Slye, who later took the screen name Roy Rogers, had just returned from a disappointing tour of the Southwest with the O-Bar-O Cowboys and were ready to give up on the music business.

“The only good thing that came out of that tour was that Roy met Arlene (his second wife) and my dad met my mom,” says Hal Spencer, Tim Spencer’s son and former president of the Western Music Association. “They went back to California to get real jobs, but Roy and my dad got together and said ‘why don’t we try this thing one more time?’”

The pair recruited Bob Nolan, who Slye had sung with in a group called the Rocky Mountaineers, and formed the Pioneer Trio in 1933. The trio moved into a Hollywood boarding house, where they practiced as many as 12 hours a day to perfect their harmonies, timing, and precision. Nolan was a prolific songwriter and brought a song to the group called “Tumbling Leaves” (later renamed “Tumbling Tumbleweeds”) that, according to the book the Sons of the Pioneers, he’d written while gazing out of his apartment window. Tim Spencer also composed many of the Pioneers earliest songs.

They built a following by performing on radio shows and soon added fiddle player Hugh Farr. When an announcer introduced them as the “Sons of the Pioneers” in 1934, reasoning that they were too young to be real pioneers, the name stuck.

The group signed a national recording contract with Decca Records, but the best way for a musical group to reach a wide audience at that time was to appear in movies. The Pioneers, who by then had added Hugh Farr’s brother Karl on guitar, signed with Columbia and appeared in many of the Westerns produced by the studio, usually as singing ranch hands.

The Pioneers appeared in about 100 films in all, including 44 with Roy Rogers, who left the group in 1937 to star on his own. They also recorded the theme song for John Ford’s the Searchers. The lineup continued to change over the years, and the group kept up an intense recording and performance schedule, spending as many as 355 days a year on the road.

The Pioneers reached a high-water mark, so to speak, with the release of Cool Water in 1959, the group’s best-selling album. But when the Beatles arrived in America in 1964, rock and roll took over the airwaves, and Western music was pushed out. The Pioneers stayed active by playing rodeos, fairs, and cowboy gatherings. And they continued to make television appearances on programs such as the Ed Sullivan Show, the Tonight Show, and the Red Skelton Hour and hosted occasional reunion shows that brought Rogers and other past Pioneers back, if only for a night.

Out of their stage clothes and sharing a post-show meal, the Pioneers keep up low-key chatter about driving so long into the night that you hallucinate tumbleweeds wearing tennis shoes and the time the group headlined a banjo festival—stories only travelling musicians can tell.

The current Pioneers are seasoned professionals who have toured and recorded with some of the top names in country and Western music. Each was recruited to fill a specific role to keep with the tradition of past lineups, whether it’s singing tenor in the core trio, playing fiddle, or rounding out the low end. And although joining the outfit means long stretches away from family and home during the annual Branson residency, each member is dedicated to upholding the Pioneer legacy.

“Each one of the gentlemen in this group has a lot at stake in Western music and are curators in preserving it,” says Boen. “It’s music that needs to live. We’re seeing parents bring kids and grandparents bring grandkids to see the Pioneers. And when I see kids sitting in the front row singing Pioneers songs, I think ‘maybe it won’t die.’”

Members have come and gone, and many have passed on, but a steadfast dedication to preserving the “Pioneer sound” remains. Lloyd Perryman, an early member who performed with the group for more than 40 years, was especially influential in creating the unique arrangements that define the Pioneer’s three-part harmony. He would coach each new Pioneer as he came into the fold.

“Give Lloyd Perryman all the credit for keeping the Pioneers going back then, and Dale [Warren] later on,” says Fred Goodwin, who produced many of the Pioneers re-released albums. “He had members coming and going, and he was always looking for that elusive sound.”

Other past members include Pat Brady, Shug Fisher, Ken Curtis, who played Festus on Gunsmoke, Sunny Spencer, and a host of other talented musicians. But, with so many members over so many years, is it still the real Sons of the Pioneers?

“We always get people asking about the originals, but the original trio only lasted three years and then they started changing, and they’ve been changing since 1937,” says Nallie. “There’s been 26 members in that length of time [excluding musicians who filled in for short periods], which is not bad for 76 years.”

“Many people have a hard time getting an idea of who the Sons of the Pioneers are these days, and a lot of people think Bob Nolan and Roy Rogers are still with the group,” says Nolen Berry, the Pioneer’s manager. “I like to compare them to the New York Yankees. Greats like Lou Gehrig and Babe Ruth aren’t with the organization anymore, but it’s still a legendary outfit with a grand tradition.”

Exposing new audiences to Western music is core to the group’s mission. The Pioneers have a few ideas to that end, including a possible tour with several other Western groups, as well as performances with orchestras, a strategy that has worked well for other Western performers.

“You’re not going to find music that’s any more American than what we sing, and it would be very sad if people didn’t listen to it anymore,” says tenor Ken Lattimore. “But people will listen to it as long as they’re exposed to it.”

Still, don’t the Pioneers ever tire of performing “Tumbling Tumbleweeds”?

“As long as I can see people out there with a smile on their face, it doesn’t matter,” says Nallie. “I’ll sing it a dozen times a day.”