Michael Jackson had "dozens and dozens" of unheard songs

Some of the material includes unused tracks from Mr Jackson's previous bestselling albums and recent recordings of songs with R&B singer Akon and will.i.am of the Black Eyed Peas.

Tommy Mottola, the former chairman of Sony Music, which owns distribution rights to Mr Jackson's music said, "There are dozens and dozens of songs that did not end up on his albums," reports the Telegraph.

"People will be hearing a lot of that unreleased material for the first time ever. There's just some genius and brilliance in there."

According to Mr Mottola the new releases of the unheard material could continue for years, "even more than Elvis".

Following the death of Mr Jackson last Thursday demand for his existing albums suddenly shot up, with the albums, "Thriller", "Essential Michael Jackson" and "Number Ones" becoming the best-selling albums of the week.

The ownership of the unheard material is not yet totally clear.

Mr 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 catalogue.

"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. I imagine that there's a ... load of concert recordings that may or may not have been released."