The string-backed ballad This Is It was released on Monday on the singer's official website and sent to radio stations. It gives advance publicity to the documentary, culled from footage of Jackson rehearsing for the concerts that he never got a chance to do.
The song's preparation is eerily similar to how the surviving Beatles took outtakes from John Lennon following his murder and added their voices and instruments to craft the Real Love and Free As a Bird songs released as part of the Anthology project in 1996.
This Is It was found in a box of tapes with only Jackson's voice and a piano accompaniment. Sony Music Entertainment isn't even sure when Jackson recorded it, and speculate it could have been around the singer's Off the Wall album 30 years ago.
Strings were added to the bare-bones recording, along with backing vocals from Jackson's brothers. Other instruments were also put in, including finger-click percussion that echoes Jackson's recording of The Girl Is Mine.
"This is it," Jackson sings to open the song. "Here I stand. I'm the light of the world. I feel grand."
The slightly unfocused composition lacks the crackle of Jackson's best work, which is probably why the song had been ignored while the singer was alive. But it has a smooth sound likely to appeal to adult contemporary radio stations and fans nostalgic for his work.
Sony says it was a coincidence that his upcoming concert series was also titled "This Is It"; the company has no evidence that Jackson himself had planned to release the song.
Posthumous releases follow a long-standing pattern in popular music dating back to Elvis Presley's death in 1977.
Presley's records have continued selling since then, with new greatest hit compilations and live concert releases finding huge new audiences. His estate still receives tens of millions of dollars each year from CD sales and other enterprises, and in 2002 he even topped the UK charts with a remixed version of an older song.
The same was true, to a lesser extent, after the deaths of rock icons such as Jimi Hendrix, Jim Morrison and Janis Joplin. A number of Lennon solo albums were also released in the years following his shooting death in 1980.
Some artists have scored major hits after their deaths. For example, Time in a Bottle was the No. 1 hit in early 1974, months after Jim Croce died. Otis Redding's biggest hit, The Dock of the Bay, was released after his death in a plane crash in December 1967. Me and Bobby McGee made the charts in 1971, a year after Joplin died.
It probably won't be the last time music fans hear something new from Jackson. Tommy Mottola, former chairman and CEO of Sony Music, told The Associated Press shortly after Jackson died in Los Angeles June 25 that there are "dozens and dozens of songs" that did not make the pop star's albums, along with more recently recorded material.
Questions about who owns the material and differing opinions among people who control Jackson's estate could complicate the release of these songs, said Rob Levine, executive editor of Billboard.
Making This Is It available online before putting CDs on sale might seem counterintuitive. But several artists do it - the Flaming Lips streamed their entire new album online - and websites such as myspacemusic.com offer streams of many songs.
Jackson's company is betting that interest generated from early release of the song will spur purchases of the album. More so than many artists, Jackson fans are more inclined to buy CDs than seek out digital copies of his music, Levine said.
"This is aimed at passionate Michael Jackson fans and people who want to participate in a historical event," he said. "In both cases, people are going to want something to hold in their hands."
The two-CD set offers previously released versions of Jackson hits coinciding with the order they are presented on the DVD. Besides "This Is It," the other new material is a spoken-word poem and demo versions of She's Out of My Life, Wanna Be Startin' Somethin' and Beat It.
Jackson, one of the most commercially successful artists of all time, is expected to sell millions of albums in the coming years. His death already brought some of his classic records back to the top of the charts.
His death at age 50 is still being investigated.
The Los Angeles County coroner has ruled Jackson's death was caused by acute intoxication by the anesthetic propofol, with other sedatives a contributing factor. The coroner found the powerful anesthetic was administered without any medical need and that recommended resuscitation equipment was missing.
