More than a dozen acts will perform in Louisiana on Sunday to benefit the fishing industry threatened by oil gushing into the Gulf of Mexico.
The event starts at noon at the Mardi Gras World River City in New Orleans.
Organizers say the concert, which will also raise funds for wetland recovery efforts, will take place rain or shine. It will feature two stages and regional seafood samples.
John Legend will be part of the lineup that includes about two dozen names.
The lineup also includes Lenny Kravitz, Mos Def, Preservation Hall Jazz Band, and Ivan Neville's Dumpstaphunk.
"It's about the people, it's about us, it's about the world. we're all in this together," Kravitz said in a video message to fans on Saturday.
An explosion aboard the drilling rig Deepwater Horizon sparked the oil spill, which has been gushing millions of gallons of crude into the Gulf of Mexico for more than three weeks.
The stakes are high for residents of coastal Louisiana who make their living from fishing in the Gulf.
"Well, if it threatens the commercial sea lanes, that's a concern because if ships don't come in and ships aren't able to go out, that stops commerce," said Donald Allee, the CEO of Mississippi State Port Authority.
BP said it hopes to start siphoning oil over the weekend.