Celine Dion and Robbie Williams are rumoured to be joining Carl Barat, Craig David, Emeli Sande, James Blunt and Rita Ora, all of whom were spotted heading to a Notting Hill studio over the weekend.
Other additional performers include Stormzy, Stereophonics frontman Kelly Jones, and Louisa Johnson.
The X-Factor winner saying of the track: “The amount of people that have actually agreed to it and gone out of their way to do it is incredible, especially how busy some of these people are.”
The huge group, which was organised by Cowell, will cover the Simon and Garfunkel song ‘Bridge Over Troubled Water’.
Directed by choirmaster Gareth Edmund Malone and featuring over 300 participants, including local residents, the single will be available to download from 8am on Wednesday.
“[Simon Cowell] is from ITV, I’m from the BBC, and it felt like a really nice message about working together,” said Malone.
“Singing absolutely cannot fix anything, a record cannot fix anything, but we might be able to raise some money, we might be able to touch a few hearts. To be frank I don’t care what it sounds like, it’s just about doing something good.”