Justin Bieber and U2 are among artists who have agreed to contribute songs to an album to raise funds for victims of the Japanese earthquake and tsunami.
Record label Universal Music said it hoped to release the digital-only album globally by the end of the week.
Bon Jovi and Rihanna have also been confirmed for the album, which will raise money for the Japanese Red Cross.
On Tuesday police said the death toll from the disaster had risen to 9,079, with 12,645 people listed as missing.
"We are doing it only digitally because it is faster," said a Universal spokesman, adding that the record would be "a worldwide release".
Announcing his involvement with the album on Twitter, Bieber wrote: "Japan needs our help... We all need to step up."
Trinidadian singer and rapper Nicki Minaj, whose album Pink Friday went to number one in the US last year, is also confirmed.
Universal artist Lady Gaga may also appear on the album, with more artists set to be announced.
The Poker Face singer has designed a "We Pray for Japan" rubber wrist band to sell to fans, with all proceeds going to relief efforts.
Last week she announced her fans had raised $250,000 (£153,000) within the first two days of sales.