(CNN) -- Michael Jackson's songs and albums went to the top of the charts in the days and weeks following his death --and there may be plenty more hits to come, if his rumored plethora of unreleased songs find their way to the public.
Rumors are swirling that new Michael Jackson material could soon be released
Since his death, rumors have surfaced about a mountain of unpublished material from the King of Pop, including recent collaborations with artists such as will.i.am and Akon, as well as unused tracks from studio sessions dating back to the 1980s.
Jackson was known to have over-recorded during his sessions, former Sony Music CEO Tommy Mottola told Time magazine. (Sony's subsidiary Epic was Jackson's label from the late '70s on, and Sony owns the distribution rights to much of Jackson's music.) He noted Jackson "absolutely" over-recorded while in the studio for his most famous albums, and that "dozens" of new albums in a variety of formats could come to fruition.
"Let's say 12 or 13 songs end up on the album; Michael could have possibly recorded 15, 20 or 30 songs," Mottola told Time. "This would probably go for every album he recorded and probably pre-dating [Sony] to his Motown days."
Mottola also said he thought some of the unreleased material made during the height of Jackson's success could be some of the star's "best work."
In addition to the material recorded years ago, Jackson also had been creating new material.
The King of Pop was working recently with will.i.am, Ne-Yo and Akon -- the Senegalese rapper who collaborated with Jackson on a remix of "Wanna Be Startin' Something," and the new song "Hold My Hand." The latter was leaked on the Internet in 2008.
"We were working on a lot of ideas," Akon told Billboard after Jackson's death. "A lot of the songs that were done were all ideas; they weren't really complete songs. He was the kind of person that wanted to lay all the ideas down [first]."
Brian May, Queen's lead guitarist, wrote on his Web site that Jackson and Freddie Mercury recorded a couple of tracks together at Jackson's house in the mid-'80s. (Mercury died in 1991.)
"Amusingly, after Freddie and Michael had spent some time together recording, Freddie came back and played us the work in progress, and he remarked that Michael had come up with a great album title ... BAD," May wrote. "A little later, Freddie smiled his wicked little conspiratorial smile, and said ... 'I have a perfect idea for our album title -- you may love it or hate it ... but think about it ... we can call it ... wait for it ... GOOD!'"
Those tracks, May said, "have never seen the light of day," though a purported song of the two has made the rounds on YouTube.
May responded to the "music thieves" but never gave a clear-cut answer as to whether the song was indeed a Mercury-Jackson finished collaboration.
"Well, there is much to be said about these 'leaked' tracks, but I'm not going to get into it right now," May wrote.
There are some reports of a secret library of 100 songs meant for his children as a personal legacy, according to Jackson biographer Ian Halperin. There has also been speculation about what could be Jackson's latest video project, called "Dome Project," which is believed to include a cemetery similar to the one in "Thriller."
That unreleased material doesn't even take into account the two albums Jackson is rumored to have been working on before his death, including a classical album with composer David Michael Frank, who told CNN that Jackson had "the tunes pretty much worked out."
So far, no details have emerged about what will become of the unreleased songs. But if his recent sales are any indiciation, music labels will seize the opportunity to release any material they have.
In the past two and a half weeks, since Jackson's death, more than 2.3 million Jackson albums have been sold, according to Nielsen SoundScan.
Jackson certainly wouldn't be the first to find posthumous music success.
In 1970, after Jimi Hendrix died, unfinished tracks, demos, outtakes and a partially completed album were left behind. Tracks by Tupac Shakur and his rival Notorious B.I.G. hit the airwaves after their deaths in the form of reimagined songs, verses and freestyles paired with beats.
And, of course, Elvis Presley's music had dramatic success after his death. One song, a remixed version of the 1968 cut "A Little Less Conversation," hit No. 1 in Britain in 2002, 25 years after Presley died in 1977.
But Jackson's legacy may eventually emerge victorious in this battle of music Kings. Mottola told The Associated Press that Jackson could by far have the most extensive collection, with enough music that releases "could go on for years and years, even more than Elvis."
CNN's Mallory Simon contributed to this report.