NEW YORK—Michael Jackson had a mountain of unreleased recordings in the vault when he died—music that is almost certain to be packaged and repackaged for his fans in the years to come.

The material includes unused tracks from studio sessions of some of Jackson’s best albums, as well as more recently recorded songs made with Senegalese R&B singer and producer Akon and Black Eyed Peas frontman will.i.am.

“There are dozens and dozens of songs that did not end up on his albums,” said Tommy Mottola, who from 1998 to 2003 was chairman and CEO of Sony Music, which owns the distribution rights to Jackson’s music. The releases, Mottola said, “could go on for years and years—even more than Elvis.”

Since Jackson’s death Thursday, there has been an enormous, almost unprecedented demand for the King of Pop’s music. The details of who owns Jackson’s unreleased music and concert footage are not entirely clear. Sony Music declined to comment. A person involved with the label who requested anonymity said no new projects or compilations are being planned yet.

The Jackson family has not publicly discussed plans for Jackson’s catalog. In a 2002 will filed in court Wednesday, the pop star left his entire estate to a family trust, with his mother and his children named as beneficiaries.

Steve Gordon, an entertainment lawyer and author of “The Future of the Music Business,” worked at Sony Music during the 1990s. He said he was at Sony when Jackson’s last contract was negotiated, though he acknowledged it could have recently been updated.

Gordon said Jackson owns some of his master recordings, while others are owned in partnership with Sony. Regardless, he said, Sony retains exclusive distribution rights for anything Jackson produced during the term of their contract.

Gordon said he expects Sony’s Legacy Recordings division to do something similar to what it did with Elvis and create a division purely for Jackson’s catalog.

“They’ve done every kind of configuration to try to squeeze more money out of the catalog with Elvis and they’ll do it with Michael Jackson — be sure of it,” Gordon said. “I imagine that there’s a ... load of concert recordings that may or may not have been released.”