When most Brits think of Asian music – if they do at all – they might conjure a twanging sitar and the high-pitched vocals of a Bollywood dance sequence blaring in an Indian restaurant, or the meditative chimes and chanting of a yoga session. In reality, of course, Asian music is a vast and diverse series of musical disciplines, and one that had been reduced, in the UK, to the reserve of anoraks and first-generation immigrants. But in the 90s, a scene came along to change all of that.

Twenty years ago, the Asian underground was born. A product of the first wave of Asian immigration into the UK in the early 60s and their children growing up in a newly diversifying society – one imbued with the racism of the National Front, as well as with a burgeoning multiculturalism from the Caribbean and west Africa – the music these first-generation British Asians made was full of internal tension. It was a mix of Indian classical instrumentals, Bollywood singing, jazz and the 90s club sounds of dub, drum’n’bass and jungle.

British Asian music since may be best remembered for its most commercial moments – Panjabi MC’s 2002 hit Mundian to Bach Ke, R&B poster-boy Jay Sean, and Cornershop’s No 1 Brimful of Asha, a reference to Bollywood singer Asha Bhosle. But the Asian underground encompassed a breadth of music on the fringes, as well as in the charts: there was the head-scratching mix of ragga, synths and Indian classical in the Asian Dub Foundation; the sitar-electronica of Black Star Liner; producer Bally Sagoo’s Bollywood remixes; and the time-stretched drum’n’bass of Tabla Beat Science. It was Talvin Singh and Nitin Sawhney, though, who were its most critically acclaimed and experimental artists.

Facebook Twitter Pinterest Talvin Singh’s debut album OK won the Mercury prize in 1999. Photograph: Michael Crabtree/PA

Both producers released their seminal albums in 1999: Sawhney’s fourth record, Beyond Skin, and Singh’s debut OK. OK won the Mercury prize in 1999 and Beyond Skin was nominated the following year. The records are very different; Sawhney’s incorporates vocal samples on his family’s migratory experience as well as jazz, Indian classical instrumentation and hip-hop, while Singh’s focuses on the dancefloor, stretching frenetic drum patterns over sub-bass and sitar.

Both have gone on to longstanding careers as composers, yet the Asian underground movement quickly faded. “I always disliked the term Asian underground,” Sawhney says. “The whole idea of the movement was that cultural change could occur and that Asians would feel they have a relevance and identity within the wider culture – that’s what was exciting. Not this idea that we were underground, but that we were part of music.”

Shabs Jobanputra, founder of the Outcaste record label that released Sawhney’s Beyond Skin, was one of the few record label executives championing this nascent scene in the early 1990s. “Outcaste started in 1994 because I wanted to see if I could form a movement to express my culture,” he says of its beginnings as a club night in west London. “Initially, it was hard to get people down to the club because it was something so different but by 1997, when we celebrated the 50th anniversary of Indian independence, 800 people turned up to our 200-capacity venue. We’d never seen anything like it.”

One of the most exciting features of Outcaste as both a night and a label was this sense of difference. “The crowd was super-mixed,” Jobanputra says. “We had Asian kids who felt they could come along and be proud of their culture, inviting their white and black friends and whoever else along without apologising.”

Coming to the UK in the 60s as a refugee from Idi Amin’s ethnic repression of the Indian minorities in Uganda, Jobanputra says he was “incredibly heartened by the reaction we got – being able to assimilate into this new culture, as well as being able to define my own sense of identity. It was a fantastic feeling to be a proud Asian person working in music.”

Facebook Twitter Pinterest ‘In the 90s I was integrating Indian classical music into everything I did’ ... Nitin Sawhney. Photograph: Jon Lusk/Redferns)

While Jobanputra and Sawhney were hosting Outcaste, across town at Hoxton’s Blue Note was Talvin Singh’s Anokha. Where Outcaste explored the jazz- and funk-influenced fringes of the underground, Singh’s Anokha was more raw, inviting punk bands to play along with his tabla sets and incorporating high-energy jungle into the mix. British Asian composer Shammi Pithia says this form of nightlife was transformative for the community. “When I went to the nights, I saw Asian people in a different light,” he says. “Usually I would associate the community with family and being at home but there, people could do their own thing and enjoy themselves like anyone else. There was a sense that this music was for us and by us, and that was very powerful.”

So why did that power fade? Jobanputra feels that the novelty of the movement’s difference wore off and the scene suffered. “It creatively ran out of steam,” he says. “I didn’t want to regurgitate the same ideas.” Instead, he now sees British Asian success in individual acts making music, rather than a collaborative movement, having signed producer Naughty Boy in 2012 – who went on to record with Beyoncé – and developing grime act Koomz. “Subcultures are needed to foster a sense of identity,” he says, “but you can’t pin the Asian identity to things as easily now because the culture has moved on. The younger generation doesn’t have any inhibition; they can be themselves without questioning. Whereas we needed something to rail against to bring us together.”

Sawhney has more controversial opinions. “After 9/11, something shifted and I didn’t hear of Asian acts in the mainstream,” he says. “It felt like a segregation took place and maybe that’s because we were having a war on a country of brown people and that made the country far more intolerant of minorities.” Sawhney says record label A&Rs are less willing to gamble on acts now: “If I was to experiment like I was in the 90s now and tried to get signed, it would be bloody tough going.”

But if we take Jobanputra’s more optimistic view, there may no longer be the need for a separate British Asian scene because integration is becoming more commonplace and acts can exist within the industry while embodying a new multiculturalism. Acts like pop-rap producer Steel Banglez references heritage in his name – the religious “steel bangle”, or kara, worn by Sikhs – but he makes music that is closer to grime and afrobeats than anything resembling the Asian underground. Similarly, rapper Premz, one of BBC Asian Network’s 2019 Future Sound winners, makes music that fuses Bollywood samples with UK hip-hop to create his own take on grime. “When we go into the studio, we don’t aim to make an Asian-sounding record,” he says, “but we’re now in a time where it’s OK to be proud of your culture, so it feels natural for me to incorporate that into my music.”

Facebook Twitter Pinterest Part of the new school ... Steel Banglez. Photograph: David Levene/The Guardian

Shammi Pithia, meanwhile, is emphatic that the underground has allowed for this embracing of marginalised identity. “Listening to Beyond Skin was revolutionary,” he says. “I realised I could mix genres in one song and I didn’t need to justify it. It’s probably the most important album I’ve ever heard since it made me realise that Indian music isn’t just for Indian people. It made me proud to be a British Asian musician.”

Perhaps, then, the shedding of the “underground” tag is a good thing: a symptom of acceptance. “Now, British Asians aren’t just underground, they’re working in all fields,” Pithia says. “Talvin and Nitin’s albums set the pathway for the music to grow far above the underground – in a sense, ‘underground’ may have been an oppressive term.” Even Sawhney admits that “in the 90s I was making a strong point of integrating Indian classical music into everything I did deliberately, but nowadays I’m at the point where if I want to write music that has nothing to do with being Asian, I can do that also.”

As such, he has been commissioned to create a new version of that most British song of all: the national anthem. “I’m travelling around the country and creating a multicultural anthem in response to Brexit,” he says. “We need to see Britain as a multicultural society now more than ever. So, I’ll use my heritage if I need to, since we can’t keep up a culture of exclusion – there needs to be representation across the whole of the mainstream.”

• Nitin Sawhney’s Brexit – A Rational Anthem for a National Tantrum, is at the Barbican, on London, 23 February.