Hundreds of popular K-pop songs have been removed from Spotify, amid a dispute with South Korean music distributor Kakao M.
Releases by popular acts including Sistar, IU, Monsta X and Epik High have vanished, leaving fans frustrated.
Spotify said its "existing licensing deal" with Kakao M had "come to an end" but it hoped the disruption would be temporary.
But the Korean company accused Spotify of refusing to extend its licence.
Kakao M is South Korea's top music distributor, responsible for 37.5% of the songs featured in the country's Top 400 Yearly Song Chart in 2020.
It also owns and operates the country's top music streaming service, MelOn, with 8.81 million monthly active users.
The dispute prompted anger from some of the artists whose work was affected.
"Why is it always the artists and the fans that suffer when businesses place greed over art?" said Tablo, the leader and producer of hip-hop band Epik High.
He said the sudden removal of their most recent album, January's Epik High Is Here (Part 1), was "against our will".
The music remains available on services like Deezer and Apple Music.
Apparently a disagreement between our distributor Kakao M & Spotify has made our new album Epik High Is Here unavailable globally against our will. Regardless of who is at fault, why is it always the artists and the fans that suffer when businesses place greed over art?— 에픽하이 타블로 | Tablo of Epik High (@blobyblo) February 28, 2021
The dispute illustrates the transient nature of subscribers' streaming libraries.
Although 60,000 songs are uploaded to Spotify every day, popular tracks can disappear overnight when the company's agreements with record labels and rights-holders expire. Users will then see songs "greyed out" in their playlists.
And it's not just Spotify - any streaming service can remove or replace music without notifying you as deals expire and are re-negotiated.
We're more used to it on video-streaming apps like Netflix and Amazon Prime, where movies and TV shows shuffle on and off the menu on a monthly basis; but music streamers tend to offer a more stable library.
In a statement, Spotify confirmed Kakao M's music was no longer available worldwide.
"Despite our best efforts, the existing licensing deal we had with Kakao M (which covered all countries other than South Korea) has come to an end," it said.
"The fact that we have not yet reached agreement on a new global deal is unfortunate for their artists, as well as for fans and listeners worldwide. It is our hope that this disruption will be temporary and we can resolve the situation soon."
However, later that same morning, Kakao M countered with its own statement, in which it claimed that Spotify had been the one who chose not to renew their agreement, even after a request on Kakao M's part.
'Billions of streams lost'
It suggested the move was linked to ongoing conversations over the availability of their music on the South Korean version of Spotify, which launched four weeks ago.
"Unrelated to the domestic contract, which we are still negotiating, we separately received notice of the expiration of our license on February 28, and we requested a renewal of our existing global contract.
"Due to Spotify's policy that they must proceed with the domestic and global contracts at the same time, our global contract has currently expired," it continued.
"We are currently continuing our negotiations about the supply of music."
Among the artists whose discographies have at least partially disappeared are IU, Seventeen, Nu'est, Mamamoo, Epik High, Monsta X, Apink, Zico, Block B, Lovelyz, Brave Girls, CNBlue, Younha and many others.
Twitter user @Lemonphobic has compiled a running list of those who are affected.
artists that had their stuff on spotify deleted, a thread— ً (@lemonphobic) February 28, 2021
Meanwhile, a fan account dedicated to boyband Seventeen suggested their total number of streams had fallen by more than 1 billion since last week.
.@pledis_17 Total on Spotify— SEVENTEEN;Streams (@svt_spotify) February 28, 2021