Jay Z, Madonna, Rihanna and Beyonce launch new Tidal streaming service
Some of the biggest names in music have launched what they're calling an "artist-owned" music and video streaming service.
Beyonce, Alicia Keys, Kanye West, Madonna, Jay Z, Rihanna, Nicki Minaj, Usher, Jason Aldean, Daft Punk and Jack White all appeared onstage in New York for the launch.
Coldplay's Chris Martin and Calvin Harris appeared via video link.
The membership-based service will provide music and video content.
The event was live-streamed on the Tidal website.
Alicia Keys gave a presentation as the other artists stood side-by-side.
She said the artists hoped the new service would "forever change the course of music history'' and ensure the viability of the industry.
She described Tidal as "a platform owned by artists" and said it would offer "exclusive experiences" but gave few actual details of the revamped service.
After she spoke Radiohead's The National Anthem was played as the artists signed "a declaration".
Jay Z's company, Project Panther, took over Sweden-based Aspiro for a reported $56m (£37m) on 13 March.
The firm owned WiMP - which rivals Spotify in some countries - and TIDAL (which streams music in HD).
Before the announcement, big names including Madonna, Rihanna, Coldplay, Usher and Jay Z's wife Beyonce changed their Twitter profile pictures to the teal blue colour of Tidal's website to show their support.
Kanye West tweeted: "Together, we can turn the tide and make music history. Start by turning your profile picture blue."
Madonna said: "Music makes the people come together. Join Madonna and turn your profile picture blue. Do it for the music."
It's been reported that Jay Z called a "summit" in February with some of the biggest names in music, including Chris Martin, Madonna and Nicki Minaj.
Lawyers and music execs were there too, to discuss streaming and, according to Forbes magazine, how to make it work better for artists.
Taylor Swift has already shown her support for Tidal by putting her back catalogue on it.
Late last year, she removed her entire music catalogue from Spotify saying there was an "inherent value placed on art" when it came to her work.
Tidal operates in 31 countries, including Britain, France and the US and is to be launched in six more including Australia and Germany.
Spotify is the industry leader and says it has 60 million users with 15 million of them paying for its services.
It has 30 million tracks available on its service and charges £9.99 per month ($9.99 in America).
Tidal streams at 1,411 kilobytes per second - well above the 320 for premium subscribers of Spotify, which offers lower levels for free users.
The difference means that Tidal offers higher sound quality for people listening on advanced sound systems.
Tidal offers users access to 25 million tracks, in addition to 75,000 music videos and other content including artist interviews.
There are two options: £9.99 for "standard sound quality", and £19.99 per month for "Lossless High Fidelity sound quality".
There is said to be no free version of Tidal beyond the initial 30-day trial period.
Tidal will compete with Spotify, Deezer and other streaming services.
Apple plans to relaunch its own Beats Music which was founded by Dr Dre.