For hip-hop fans, the debate about whether lineup or festival identity is what pulls in the punters is a relatively new one. While hip-hop riding high in mainstream UK festival lineups is hardly news – Jay-Z decisively made the point back in 2008 that fans will bob their heads in a field to live hip-hop (and like it), and now bookers trip over themselves to secure big names across the UK. You want Busta Rhymes on the Isle of Wight? Danny Brown at Worthy Farm? Last year even rock-heavy Reading added a Radio 1Xtra stage which invited Giggs, Action Bronson and Chance the Rapper, while this year sees Drake and Kanye at Wireless and Nas and A$AP Rocky at Lovebox.

UK hip-hop festival Boom Bap, started in 2012, prides itself on being an alternative to the mainstream. Ivan Andrade is the man behind one of the biggest niche hip-hop festivals in the UK.

Andrade works with a team of over 30 promoters and labels from the UK hip-hop scene to ensure the festival maintains a very specific hip-hop identity. "We're the first hip-hop festival dedicated to less mainstream and commercial hip-hop," says Andrade. "I was really surprised that there wasn't a festival like this already in the UK. We're part of the growth of the UK hip-hop scene so the aim is to support the scene as well as have a good time."

There appears to be a market for it. The festival has steadily grown since its inception two years ago, and this year is en route to selling out. Andrade is confident that the identity of Boom Bap will draw fans – along with showcasing lesser known talent, other features of the four elements of hip-hop are incorporated, with DJ bookings, live rap battles and professional graffiti artists.

Andrade and his collaborators began running UK hip-hop events of the same name a few years ago, and tried their hand at a festival after feeling uninspired by mainstream offerings. "I saw Nas at Nass Festival. It was frustrating because I felt it went over a few peoples heads," Andrade recalls. "There's something weird about sandwiching Nas alongside Katy B."

While US rap may be more commercially viable for selling out larger crowds, Boom Bap prides itself on proving there's a market for a more purist UK hip-hop festival with no need to sandwich. Certainly the line-up beyond the US headliner, Wu-Tang Clan's Ghostface Killah, offers few handholds to an outsider not au fait with the scene. While there are iconic UK hip-hop acts such as Chester P, many may struggle to name hits from the likes of Frosty or Annihilate (though names like Hayze and Smellington Piff do give a sense of the clientele). Andrade argues that there's a market for UK hip-hop despite the lack of big names. "I'm not scared of being called a hip-hop purist – I don't think that's true though. I listen to Drake as well as the likes of Task Force! It's true that, with our line up, you have to dig a little bit deeper… but that's what the underground is all about, I guess."

But just how commercially viable is a strong underground identity? The festival website states that "'2014 is the year that Boom Bap goes international" – is Ghostface's presence as the headliner evidence that the UK genre on its own can't bring numbers in? Or an indication that big US names can sit alongside UK underground acts in hip-hop harmony? Could the UK one day have a hip-hop festival near the scale of the US extravaganza Rock The Bells?

Jehst is an artist at the forefront of UK hip-hop, and is proud to see the scene represented. "It would be impossible to put on an all-encompassing hip-hop festival in England, so I support what festivals like Boom Bap are trying to do. While I'm not in favour of keeping the scene totally UK hip-hop centric, I do question why, if your USP is UK hip-hop, you'd have a US headliner. Especially as the UK scene is so healthy right now. I think a lot of hip-hop is undergoing an identity crisis as it gets bigger and infiltrates the pop world. Niche festivals may or may not be the answer, but if they are, then they need to strengthen their individual identities."

"We never started out wanting to be a 'just UK hip-hop' festival, even though the music we showcased was predominantly UK hip hop," argues Andrade. "At the same time there were also DJs playing 808 and trap. We felt a US headliner would be a good way to get fans in who weren't necessarily fans of UK hip-hop."

DJ Snips is one of the founders of hugely successful London hip-hop night Livin' Proof. Their events showcased US artists like Danny Brown and A$AP Rocky back when they were unknown underground rappers. "People sometimes tend to file rap as being either mainstream or underground," he says, "when actually, it's about what's exciting at the time. There's a place for big-name artists to sit alongside the lesser-known ones, and you don't need to have a lineup dominated by artists that people don't know to make that point. We represent G-funk, trap, 808 sounds, Boom Bap sounds, because there's more to the genre than the confines of UK hip-hop. If we did a festival we'd have both American and UK artists and it would just reflect the current state of hip-hop everywhere. Our demographic might be too small in the UK to have a Rock The Bells equivalent but it would be amazing."

Snips is skeptical of equating 'niche' with authenticity. "A lot of hip-hop fans can be obsessed with 'realness', but what does that even mean? It can feel really contrived because attending a festival that only plays UK hip-hop doesn't make the point that you understand a culture better than someone who goes to Wireless."

Tinie Tempah came from the then-niche grime scene but ascribes some of his success to his visibility at big festivals. This year he's playing at Wireless, third from top billing below Kanye and Pharrell. "If you're not getting a lot of gigs or bookings, then a festival is always a good place to showcase a specific genre," he says. "When I first performed at Wireless five years, ago I was on the Turbo stage, which was tiny, but it was a way for me to bring my small fanbase together and perform alongside much bigger stars. I would have gone to a grime festival back in the day if they existed, and part of me misses that, but the best festivals are eclectic."

Eclecticism might not be tempting over those diehard hard hip-hop fans who'd prefer a festival that purports to be 'real' over the glossy corporate alternatives where hip-hop is wedged between huge pop stars and rock acts. And with UK hip-hop having decidedly less sway with festival bookers than big US acts, Boom Bap's championing of a scene that gets little representation is worthy of celebration.

"I think we're obviously not the typical mainstream festival, we represent a more underground side of hip-hop culture. There will always be people who aren't catered for in the mainstream. We try and showcase anything fresh and exciting," says Andrade. "We hope that we'll continue to grow, showcasing artists we feel are really killing it."

There's no one answer to the future of hip-hop at UK festivals. Jehst sums it up: "An underground will always exist. There will always be the artists that sell high numbers and there will always be people who are passionate about pushing the artists that don't – for the ones that don't, the festivals probably can't grow much bigger and the artists probably aren't growing their mainstream audiences that much… but maybe that's what the fans want."