Cowell organised the single in days
The all-star fund-raising single for the Haiti earthquake victims has been played on radio for the first time.
More than 21 artists contributed to the cover of REM's Everbody Hurts, including Take That, Susan Boyle and Kylie Minogue.
Pop mogul Simon Cowell hastily arranged the record, which will be available to download on 7 February.
Leona Lewis opened the track, followed by Rod Stewart, Mariah Carey, Cheryl Cole, Mika and Michael Buble.
Parts of the song were recorded in London, while artists - including Robbie Williams - put down their vocals in Los Angeles.
Artists such as James Morrison and Alexandra Burke sang their lines at Trevor Horn's Sarm Studios in Notting Hill - where the original Band Aid single was recorded in 1984.
Among others whose voices can be heard on the record are Susan Boyle, Miley Cyrus, James Blunt, Jon Bon Jovi and members of Westlife and JLS.
Cowell said making the record had been "an absolute priority for us all".
Half of the single's proceeds will go to the Sun's Helping Haiti fund and the rest will be donated to the Disasters Emergency Committee.
In the US, an album of artists who performed at George Clooney's fundraising telethon, including Madonna, Jay Z, Rihanna and Mary J Blige, has been released on iTunes.