Music festivals fail to reflect the diversity of the UK music scene, with headline slots being dominated by a small band of male rock acts over the decades, a study suggests.
Some eight out of 10 top slots were occupied by all-male acts, analysis of more than 600 headline appearances across 14 major festivals found.
And a quarter of all headline slots were taken up by the same 20 acts.
The study comes as 175,000 people head to the Glastonbury Festival.
Musician and writer Emma-Lee Moss said the music industry was "skewed towards a male demographic".
She said: "If we continue talking - and we continue investigating and agitating - hopefully, naturally, things will become more inclusive.
"We have got such amazing musicians in the UK who are women. What about a festival that wasn't just women-led headliners, but also most of the bands?
"It's not just the headliners that are imbalanced, it's acts all across the board, and we all know there are people making music that are not just white men. If someone decided to reflect that in their line-up, they'd be celebrated."
Who is in demand?
Male rock acts such as Muse, Kasabian and The Killers dominated the festival headline slots in our analysis. Twenty acts - or about 6% of the 308 acts in our sample - took up 24% of all headline slots.
Dr Simon Warner, a popular music researcher at Leeds University, said: "There remains a small number of groups who can actually generate consumer interest, and I think it's down to sheer economics.
"If you are going to get 80,000 you need to have acts that can get [punters] to spend cash. If you are spending hundreds of pounds, you are not going to go for an indie band, you are going to go and see the Red Hot Chili Peppers or whoever."
And there was a stark gender imbalance.
In our study, only 37 headline performances involved all-female acts, while 68 were bands of mixed gender.
Rihanna was the only female act to clock up four top slots. She was followed by Florence and the Machine and Grace Jones, with three headline slots each.
Michael Baker, of the publication Festival Insights, which runs the UK Festival Awards, said: "Some festivals do attempt to address gender imbalance, such as Field Day, whose curator recently told me that they failed to book 50% female acts because there simply weren't that many available."
To promote diversity, festival organisers need to foster and promote emerging talent, he said.
"Festival organisers are aware of the lack of interesting acts at the top, and many have taken to differentiating themselves from their competitors via non-music activities," he said.
"What needs to happen, however, is more long-term thinking and effort applied to the representation and promotion of emerging talent at festivals."
The lack of women headliners was reflected not just in traditional rock festivals, but at more pop focussed events such as V and Wireless.
Why such a reliance on guitar bands? Mark Savage, BBC music reporter
As Prince once put it, there's joy in repetition.
If you're tired of Radiohead playing Street Spirit, or The Killers bashing out Mr Brightside, then you're either not a fan or (more likely) a member of the band.
But there is a worrying reliance on white, male guitar bands at music festivals - which is strange, because white, male guitar music is massively out of favour.
The charts are dominated by pop and hip-hop, with acts like Justin Bieber, Rihanna, Stormzy, Ed Sheeran and Taylor Swift dominating streaming services. If bookers took a risk on these acts, they'd undoubtedly attract a younger, more passionate crowd - ensuring their longevity in the process.
Of course, no-one is going to do that when heritage rock bands guarantee ticket sales. Festivals are already taking a financial risk - why take on more?
The V Festival is an honourable exception. Born in the midst of Britpop, it's re-positioned itself as a festival for pop connoisseurs, booking acts like Calvin Harris, Beyonce, Rudimental, Olly Murs and P!nk as headliners. It's proof that audiences will embrace diversity - in gender, in genre and in the race of their artists - if they're given the chance.
Hopefully others will take note. And when they do, it's our responsibility as fans to make it work.
Are people still listening to rock?
Success on the music streaming service Spotify does not guarantee top dog status on the festival circuit.
Drake, Ed Sheeran, Justin Bieber, Nicki Minaj and Rihanna were the most listened to on Spotify, but had just nine festival headline slots between them.
The most listened-to tracks from our sample of headliners came from the world of mainstream pop, hip hop and dance.
- Ed Sheeran - Shape of You (Glastonbury, 2017)
- Bruno Mars - That's What I Like (Wireless, 2014)
- Kygo and Selena Gomez - It Ain't Me (Wireless, 2016)
- Calvin Harris - Slide (Wireless, 2016)
- Kygo and Ellie Goulding - First Time
- Coldplay and The Chainsmokers - Something Just Like This (Glastonbury, 2016)
- Drake - Passionfruit (Wireless, 2015)
- Ed Sheeran - Perfect
- Calvin Harris - Rollin
- Ed Sheeran - Castle on the Hill
And it appears the dominance of hip hop and pop on streaming services is changing the make-up of festivals.
Based on Spotify's classification system, the proportion of headline acts in our sample described as being indie and rock has been in decline since the 1990s, at the same time as hip hop and pop acts rise.
Though, as 1990s pop duo Daphne and Celeste can attest, rock fans do not always appreciate pop invading its territory. The pair were faced with a barrage of boos and bottles when they took the main stage at Reading Festival in 2000.
Some 94% of headline acts hailed from the UK, the US and Canada.
London was the music capital in the UK, producing most headline acts, followed by New York, California, Manchester and Glasgow.
Mr Baker said: "Our tiny nation alone exports a massive amount of the world's most popular music."
Age no barrier
The average age of a festival headliner is 39. The V Festival, held in Essex and Staffordshire at the end of August, had the youngest headliners with an average age of 32.
The Rewind Festival, which showcases bands from the 1980s and is held at three sites - Berkshire, Cheshire and Perthshire - in August, had the oldest headliners with an average age of 56.
And Glastonbury headliners have been getting older.
More about this story
BBC England's data unit analysed more than 600 separate headline performances across 14 UK festivals. They were Download, Reading/Leeds, T in the Park, V Festival, Isle of Wight, Bestival, Latitude, Wireless, Rewind, End of the Road, Cornbury, Boardmasters and Lovebox.
Festivals that were not defined around headline acts were excluded. These include Creamfields, Boomtown Fair and Womad. Fairport's Cropredy Convention was also excluded as it is traditionally headlined by its organisers.
Read more about how the story was put together here.