20 unfinished Michael Jackson tracks stored on sound engineer's computer

The singer hadn't sung the choruses for the tracks, so "someone would have to be found" to perform them

Michael Jackson's sound engineer said Thursday he has 20 unfinished tracks by the late pop star on his computer -- but he isn't allowed to let anyone hear them.

"I don't have the right to write the song titles or to let people hear them for the moment," Michael Durham Prince told the French newspaper Le Parisien.

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Months after Jackson's death in 2009 from a lethal overdose of sedatives, the entertainer's estate signed a $200-million deal with Sony recording company, according to the Wall Street Journal.

Under the agreement, Sony can bring out up to seven albums over a decade, including new or remixed Michael Jackson songs. Two posthumous albums have already been released, in 2010 and 2014, but Sony told AFP on Thursday that no others were currently in the works.

Prince, who was Jackson's audio engineer from 1995 up to his death, told Le Parisien in an interview from Germany: "I have on my computer 20 unreleased (songs) by Michael, all of them unfinished".

He explained that Jackson hadn't sung the choruses for the tracks, so "someone would have to be found" to perform them whenever they did get released, if Sony and Jackson's family gave the go-ahead. "That would mean duets," he said.

Prince added that he believed there would be further Michael Jackson albums in the future, "but for the moment, we are thinking more about bringing out new songs every six months".

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Jackson died aged 50 on June 25, 2009 as he was readying to give a series of concerts in London.

His personal doctor, Conrad Murray, was jailed in 2011 for involuntary manslaughter but served only half of his four-year sentence because of prison overcrowding and good behaviour.