Two teenage rock musicians from rural north Wales are celebrating after becoming the first band to pass one million plays with a Welsh language song on the streaming service Spotify.

Dion Jones and Sion Land, 18, were stunned when their song Gwenwyn (Poison) surged towards and then past the million mark. The pair, whose band is called Alffa (Welsh for Alpha), have picked up fans not only from across the UK and the US but in countries such as Brazil, Mexico and Poland.

Jones and Land, who only left the sixth form in the summer, will invest the funds in the recording of an album, and are hoping their success may lead to overseas tours and festivals.

“It has been amazing,” said guitarist and lead singer Jones. “It’s really weird to think people are listening to our music all over the world. That’s a bit scary, really.”

The duo’s first language is Welsh. “It’s natural for us to sing in Welsh,” said Jones. “Actually, singing in English is harder. It’s good that this may help break down language barriers. It’s not just about our music, it’s brilliant for the Welsh language.”

Jones and drummer Land formed the band while studying together. “We were mates through music and then thought it was time to form a band,” Jones added. “We played gigs locally, then around Wales. Now it’s really kicking off.” The pair will not talk about the deeper meaning of the song. “There’s a story behind it but we tend to keep it to ourselves,” he added.

The band were chosen to take part in a project called Horizons, a collaboration between BBC Wales and the Arts Council of Wales to promote new Welsh music.

Gwenwyn was recorded in the Ferlas Studio in the Snowdonia National Park and released in July. Distributor PYST managed to get it on to Spotify playlists Walk Like A Badass and The Rock List, alongside artists such as Arctic Monkeys, The Strokes and The White Stripes.

Alun Llwyd, the chief executive of PYST, said: “What’s beautiful is that Spotify judge the songs on music merit, not the language or the band. Nobody knew Alffa outside a small part of Wales. This is testament to the strength of the song.”

There are beloved rock and pop bands who have sung in Welsh including the Super Furry Animals, Gorky’s Zygotic Mynci and Datblygu.

An annual Welsh language music day now takes place, led by the devolved government as part of its long-term vision to get a million people speaking and using Welsh by 2050. Last year’s event featured live Welsh music at events across the country and as far afield as Budapest and Brooklyn.

Llwyd argued the Welsh language pop and rock music scene is the strongest it has been for years and includes genres ranging from folk to electronica. “There’s a massive, organic growth thanks to the digital revolution. Streaming has made it more of a level playing field. The fact that Alffa sing in Welsh has no bearing on how far their music can travel, something that seemed impossible for a minority language in years gone by. This is just the beginning.”

Yws Gwynedd, from Alffa’s record label, Recordiau Côsh, said he felt lucky to be working in the Welsh music scene at such a time. “Language barriers are being blown wide open,” he said.

The band’s Spotify success will not change their lives. “People keep on going on about money,” said Jones. “For us it’s about trying to make an album. Every penny will be invested in doing that.”