The event will take place on Saturday in Wales. Christina Aguilera, Smokey Robinson, Gladys Knight, Leona Lewis and Cee Lo Green are on the bill for Saturday's "Michael Forever" show at Cardiff's Millennium Stadium.
Oscar-winning actor and singer Jamie Foxx will serve as emcee.
Chris Hunt, chief executive of event organizer Global Live Events, said Wednesday that the concert would be a "fantastic evening," despite the absence.
The pop star's mother, Katherine Jackson, and other relatives are scheduled to attend. However, the show is not affiliated with Jackson's estate.
Organizers have withdrawn an offer to the band Kiss over singer Gene Simmons' past criticism of Jackson.