Jay Z, 43, said he will bring a modern "Jazz Age" energy to the soundtrack, which will feature "the world's top musical artists", reported Los Angeles Times.
Luhrmann and Jay-Z were introduced by DiCaprio, who plays the lead role of Jay Gatsby in the adaptation of F Scott Fitzgerald's novel set in the roaring 1920s of America.
The rapper worked with Luhrmann and composer Craig Armstrong on the music in the film for two years.
"'The Great Gatsby' is that classic American story of one's introduction to extravagance, decadence and illusion. It's ripe for experimentation and ready to be interpreted with a modern twist," he added.
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The film is set to open the Cannes international film festival this May with Jay-Z and Bachchan attending the mega event.
'The Great Gatsby' is a classic story of love, glamour and excess of the roaring 1920s of America.
The Warner Bros movie follows Nick Carraway as he lands in New York City in the spring of 1922 to chase his dreams of becoming a writer.
Unknown to him, Nick will play an important role in the meeting of two star-crossed lovers and the eventual ruin of Gatsby.
DiCaprio plays the elusive Gatsby, while Mulligan stars as Daisy Buchanan. The story is told through Tobey Maguire, who plays Daisy's cousin Nick.