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. "People will be hearing a lot of that unreleased material for the first time ever. There's just some genius and brilliance in there."
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. Nielsen SoundScan said Wednesday that three of his records - "Number Ones," "Essential Michael Jackson" and "Thriller - were the best-selling albums of the week, and 2.3 million tracks of his have been downloaded in the U.S. alone.
When a music star of Jackson's stature dies, labels typically comb through their archives to pull out anything they can release. New compilations of recordings by performers such as Elvis, Tupac and Jeff Buckley are still released nearly every year.
Mottola, who has described himself as the "shepherd and gatekeeper" of Jackson's catalog and is familiar with it better than anyone, said that for every album Jackson made - including classics like 1979's "Off the Wall" and 1982's "Thriller" - he recorded several tracks that didn't make it onto the records.
(Mottola had only laudatory things to say about Jackson, who criticized Mottola in 2002 as a racist. Among those who defended Mottola at the time was the Rev. Al Sharpton.)
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."
Jackson's last original album was 2001's "Invincible." His 2005 child molestation trial and other controversies distracted him from recording, but he was active in recent years.
He died just weeks before he was to perform 50 concerts at London's O2 arena in what was supposed to be his comeback. He had also begun working on new material.
Two weeks before he died, he wrapped up work on an elaborate production dubbed the "Dome Project," which could be the final finished video piece overseen by Jackson. Two people with knowledge of the project confirmed its existence Monday to The Associated Press on condition they not be identified because they signed confidentiality agreements.
Four sets were constructed for Jackson's production, including a cemetery recalling his famous "Thriller" video. Shooting for the project lasted from June 1 to June 9. Now in post-production, the project is expected to be completed next month.
Last year, Jackson released "Thriller 25," an album marking the 25th anniversary of the album. It included the new song "For All Time," as well as five remixes that involved will.i.am, Kanye West, Akon and Fergie.
The Black Eyed Peas frontman will.i.am has said he and Jackson recorded several songs together. He told the BBC on Monday that Jackson had possession of their demos, and that the songs "demanded all the people to the dance floor."
Akon had hoped to complete an album with Jackson once he finished his London concerts. The singer said they used to meet in Las Vegas whenever they had the time, and would talk on the phone constantly about ideas for the album.
Akon said they never actually completed a song except for "Hold My Hand," which leaked last year. "All the other songs were just ideas," Akon said.
He said he will keep the song fragments - a chorus here, a verse there - "locked up in the vault" until the Jackson family decides how to proceed. He said it could be worked into a tribute album.
"It was all positive records - songs to uplift people, songs to make people think about the problems in life," Akon said. "It was all about bringing people together."