The lyrics and music are an updated version of "We Are the World," a song that raised at least $30 millions for African humanitarian programs 25 years ago.
Lionel Richie, who co-wrote the first song with Michael Jackson, is organizing the effort. The original producer, Quincy Jones, is using the same studio he used in 1985.
Smokey Robinson, who sang on the original, said the roster of 100 singers asked to take part does not include any of the 45 stars from the previous version.
While the list has not been made public, CNN has confirmed it includes Usher, Carrie Underwood, Fergie, Jason Mraz, Rob Thomas, Anthony Hamilton, Trey Songz, Sugarland, Julianne Hough, India.Arie and Musiq Soulchild.
Many of the stars were already in Los Angeles to attend Sunday's Grammy awards show.
One tool Jones used in 1985 to keep the massive recording session from getting out of control was a sign above the studio door that read: "Check your egos at the door." It is expected it will be there again, one organizer said.
Organizers have not said when the song might be ready for the world to hear.