Image copyright AP Image caption Hundreds of unreleased Prince songs have circulated on bootlegs, but there is thought to be much more material to sort through

Prince's infamous "vault" of unreleased music is being shopped around record labels with a price tag of $35m (£29m), according to US reports.

The trove contains songs like Rebirth of the Flesh, Electric Intercourse and Extraloveable - which have been widely bootlegged, but never formally issued.

It also contains hundreds of hours of live recordings and concert footage.

All three major labels are understood to be in talks over the material, according to Billboard magazine.

Quoting an unnamed source, the magazine said a deluxe edition of Purple Rain - which was announced in 2014 but never materialised - was now likely to be released in 2017.

A new greatest hits compilation is also due before the end of the year.

Media playback is unsupported on your device Media caption Prince's former engineer Susan Rogers on the origins of the vault

The infamous vault is tucked away in the basement of Prince's Paisley Park home in Minneapolis.

Accessible by lift, it is a climate-controlled room hidden behind a steel door, complete with a combination lock and large spinning handle.

The late singer was the only person with the code to open the safe. When he died in April, it had to be drilled open by the company responsible for his estate.

'Comical songs'

According to the singer's former recording engineer Susan Rodgers, who started the vault for Prince during the 1980s, the facility was almost full when she left in 1987, with songs in there that pre-date his legendary Purple Rain album.

She said the tapes contained everything from late-night jam sessions to intensely personal songs that the artist felt uncomfortable releasing.

"If he wasn't taking care of conducting business... or if he wasn't dating or seeing someone socially, which would be less often than you might think, for the most part, Prince had an instrument in his hands and he was playing music," she said.

Image copyright AP Image caption Professionally-filmed footage of the star's Purple Rain tour resides in the vault

Brent Fischer, who composed string arrangements for the star alongside his father Clare, said the archives were vast.

"I think over 70% of the music we've worked on for Prince is yet to be released," he told the BBC.

"There are lot of songs that were sent to us clearly with the idea that they would never be released. They were almost comical songs that he would work out with his horn players. There was lot of wild horn parts and experimentation with samples."

However, the ownership of the music is unclear. Much of the material was recorded when Prince was under contract to Warner Bros, and he subsequently signed one-off deals with every other major label, several independents and Jay-Z's Tidal streaming service.

The musician died from an overdose of the painkiller fentanyl in April without leaving a will.

Courts have still to decide how to divide up his estate, with several potential heirs coming forward in the months after his death.

A tribute concert to the star will take place in St Paul, Minnesota, on Thursday, featuring performances from Stevie Wonder, Christina Aguilera, Chaka Khan, Tori Kelly and Prince's first wife Mayte Garcia, among others.

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