The development of electrical sound recording in the early 20th century in the United States opened the door for a multitude of musicians to share their talents with an exponentially larger audience. Record labels sent talent scouts across the country in hopes of discovering new acts to showcase, and in the process they helped lay the foundation for many genres of music that remain popular today.

That’s the basis for the documentary “American Epic,” which had its U.S. premiere at the Hawaii International Film Festival in 2015, won awards at film festivals in the U.S., Canada and Australia last year, and makes its broadcast premiere this month as a three-part series airing on PBS.

While most of the documentary focuses on musicians from the continental United States, producers Allison McGourty and Duke Erikson, along with director Bernard MacMahon, knew they also wanted to focus on what at the time was known as the Territory of Hawaii.

“The thing is, Hawaiian music had this enormous influence in America,” MacMahon said in a phone interview from his home in Southern California. “It permeated across the whole country on an absolutely vast, viral level. It became so much a part of the American musical culture that people no longer recognized it as Hawaiian.

“It was like the sugar in American music at the time. There was so much of it out there that people didn’t realize it came from the islands.”

One of the instruments that defined that sound was the steel guitar, invented by a Hawaiian who went on to enjoy international success as both a performer and educator.

Born in 1874, Joseph Kekuku was 11 years old when he developed his slide technique after finding a loose bolt on railroad tracks and sliding it over the strings of his guitar, according to historical accounts documented in “Hawaiian Music & Musicians” by George S. Kanahele and Honolulu Star-Advertiser reporter John Berger.

After trying to substitute a penknife and the dulled edge of a straight razor for the bolt, Kekuku moved on to hair combs and drinking glasses before he ended up making his own steel slide — nearly identical in design to those used today — in the metal shop of the Kamehameha School for Boys while enrolled as a student.

Kekuku left for the mainland in 1904 and did not return before his death in 1932. He traveled the country with performance troupes and taught others his playing technique, and also toured in Europe. It was there he contributed to what likely is the only recording in existence that clearly features him performing.

“I tracked down a 1930s guitar and banjo magazine, and in it was an interview with someone named C.S. Delano who played with Kekuku when he was in London,” said MacMahon. “Delano mentioned that his friend Joseph had actually made a proper studio recording with an African-American duo who came from the South to Britain and became hugely popular.

“For some reason, that recording was incredibly hard to find. It took me two years to track down copies. His name wasn’t on it, but when I put the record on you could hear there was a big steel guitar solo in the middle.”

It’s this recording that MacMahon brought in 2015 to the Polynesian Cultural Center, where a statue commemorating Kekuku was unveiled. He played it for family members who had never heard their relative’s music before, creating what MacMahon described as one of the more remarkable scenes in “American Epic.”

“Basically, this Hawaiian guy from Laie effectively changed the sound of world music,” MacMahon said. “In a way, Kekuku was really a precursor for everything. He was the first musician coming from an ethnic background, from a remote place, who had this really profound effect before all the other musicians came along. He was the first one. He was a trailblazer.

“When he went to Mississippi, all the blues players heard what he was doing and started incorporating slide guitar into their music. The steel guitar you now hear in country music is from Kekuku. And that led on to its usage in rock and, similarly, African music. African artists like King Sunny Ade, the slide guitar they use is all based around what Kekuku invented.”

Along with “American Epic,” PBS will air “The American Epic Sessions” at 8 p.m. June 6. The companion feature film showcases musicians of today replicating the recording process used a century ago with vintage equipment from that era. A companion soundtrack, 100-song box set and additional archival recordings will be released this month in both digital, CD and vinyl formats.

“American Epic” airs at 9 p.m. May 16, 23 and 30 on PBS. Visit americanepic.com for more information.