Michael Jackson's 'This Is It' Single Debuts Online

New song appears twice on soundtrack to upcoming documentary.

The new [artist id="1102"]Michael Jackson[/artist] single, "This Is It," debuted online at midnight on Monday (October 12), with some instantly speculating that the heartstring-tugging song could become one of the late pop star's best-selling singles of all time. The spare, mid-tempo love ballad, which was reportedly recorded during the sessions for his 1991 Dangerous album, finds Jackson in classic voice, singing in his clear falsetto along to finger snapping, a subtle jazzy piano and swelling strings, as his brothers, the Jacksons, provide ethereal backing vocals.

For almost four minutes, Jackson weaves one of his pleading tales of unrequited love, opening with the lyrics "This is it, here I stand/ I'm the light of the world, I feel grand/ Got this love I can feel/ And I know, yes, for sure, it is real." Jackson goes on to tell his unnamed lover that he feels as if he's seen their face "a thousand times," and, eerily, that "I know that you have got addicted with your eyes/ But you say you gonna live it for yourself."

Jackson died on June 25 of an overdose of the surgical anesthetic propofol after years of allegedly suffering from a prescription-pain-medication addiction.

The new song is currently streaming on the singer's official site, and it will play over the credits of the documentary of the same name, which hits theaters October 28 for a limited two-week run. The track will appear twice on the two-disc soundtrack to "This Is It," as both the vocal version and an instrumental take. The soundtrack, with a handful of previously unreleased versions of some of Jackson's classic hits, will go on sale October 27.

The song was reportedly written in 1980, which might explain the lyrical similarities to some of the yearning hits on Jackson's early solo albums like Off the Wall and Thriller, including the urgent refrain "I never heard a single word about you/ Falling in love wasn't my plan/ I never thought that I would be your lover/ C'mon, baby, just understand." The simple arrangement and quasi-messianic lyrics ("I'm the light of the world"), though, betray it as a late-period song, more in line with such emotional ballads as "Man in the Mirror" and "Gone Too Soon," from, respectively, 1987's Bad and Dangerous.

"This Is It" may be the first of many previously unreleased Jackson songs that will be issued in the wake of the singer's death, with reports that there are 100 or more tunes in the vault that fans have not heard.