Bob Harris on the golden combination of Dolly Parton, Linda Ronstadt and Emmylou Harris

Veteran broadcaster Bob Harris has spent decades championing the genre in the UK, and after winning awards from the Country Music Association, the Americana Music Association, appearing on stage at the Ryman Auditorium and guest-announcing at the Grand Ole Opry, says he's now better known in Nashville than in the UK. Since presenting the Old Grey Whistle Test in the Seventies, he's got to know all three of the Sisters in Country well, and remembers their collaborations as "magical".

"Trio is a beautiful thing to listen to," he tells me at BBC Western House, where he records both Bob Harris Country (Thursdays, 7pm) and Bob Harris Sunday (Sundays, 2am) on Radio 2. "Back in the Eighties, the mainstream sounds of the era were synthesisers, and everything was very artificial. Trio and its natural 'mountain music' sound really stood out. Anything that was successful in the mid-80s and cut across the grain of other music being made at the time had an impact. I think without feeling that what they were doing with Trio was influential, it was. It broke the mould, and it soared to the top of the Nashville charts."

The artistic backgrounds of the three women were diverse: Dolly was raised on traditional Appalachian music; Emmylou was an established folk star and Linda was a firm fixture on the California rock scene. But, Harris says, “Those three iconic women joining together was a golden combination. Normally only sisters can harmonise like Dolly, Linda and Emmylou do.” He shares his memories of the trio, and why he thinks, decades on, their influences endure.

“You think that Dolly Parton is a country artist, which she is – she’s a Tennessee girl, brought up in the hills, with a dirt-poor family, and country and bluegrass is the blood that runs through her veins. But she transcends. You can put her on a stage anywhere, and she’s a trouper, she knows absolutely how to get an audience on her side. She’s still so fresh, open, and natural, there’s still almost a naivety about her. We saw all of that during her performance at Glastonbury – who would ever think that Dolly Parton and Glastonbury would make such a fabulous combination? But they did, and she totally won the crowd. I don’t know anybody that doesn’t absolutely love Dolly Parton.”

“Linda and I met at the time of Whistle Test, she was having huge hits in America that took her to the top of the charts. She came over to play a concert and I remember backstage was a who’s who of rock stars. Keith Richards turned up, Jackson Browne was there, and it was an amazing night. There weren’t that many women that were really successful in the charts, so Linda was very special to the LA music scene – and the American music community. Her coming over to the UK, and us filming her, was a very big deal. Linda is an articulate voice in looking back at her connections with Dolly and Emmylou especially, and expressing the emotion that they all felt.”

“The first time Emmy and I met was in the mid-Seventies. She came over to the UK to do Whistle Test, we got on great, and she and I have been really good friends ever since. One of the things that characterises Emmylou’s way is her generosity – she is incredibly generous of spirit, and she’s particularly willing to reach out and help young artists. She appears on their albums, supports them on their tours, if there’s somebody new and young that she likes, she steps forward and gets behind them in an amazing way. She's one of the foremost country music artists, whose credibility is unimpeachable, She’s Nashville royalty. I was awarded the Trailblazer Award at the 2011 Americana Music Association Awards, and it was presented to me by Emmylou. It was one of the biggest honours of my entire life.”

Now, there's a new wave of women shaking up country music, because, Harris says, there's a young energy from artists like Kacey Musgraves – whose Royal Albert Hall concert airs tonight – that gives the genre new vitality.

28-year-old Texan Musgraves has won acclaim for combining traditional country musicianship with a decidedly millennial social conscience. Her songs deftly approach topics like homosexuality, recreational drug use and casual sex with disregard for the staunchly conservative Southern Bible Belt that makes up much of country's listeners, and won her two Grammy Awards in 2014 – Best Country Song for Merry Go Round and Best Country Album for her debut Same Trailer Different Park – and a slew of other nominations since for last year’s follow-up, Pageant Material.

"One could talk about Kacey for hours," says Harris. "She's gorgeous, she writes songs that resonate with fans who love her, she reaches outside her genre, even though her music is firmly rooted in traditional country. Her stage sets put her in a glitzy country bar and she wears tassels and boots, but she couldn't be anything other than 2016. She's a perfect access point for country music now – hers is music that's acknowledging and pulling in influences from the past, but looks into the future. We're very fortunate right now to have a new generation of incredible women country stars. There’s Kacey in particular, and Miranda Lambert is the real thing. Ashley Monroe, Brandy Clark, Angaleena Presley… All these women are bringing country music to a new generation of girls who connect with the songs they're writing."

The Complete Trio Collection, by Dolly Parton, Emmylou Harris and Linda Ronstadt, is on sale now from Rhino.