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Nancy Bundt
Prince's estate has released the star's original 1984 recording of Nothing Compares 2 U, ahead of the second anniversary of his death.
One of Prince's loneliest songs, it was initially given to his side project, The Family, before Sinead O'Connor made it a hit in 1990.
Prince later reclaimed it in concert, and released a live version of the ballad on his 1993 Hits album.
The song also featured in his last ever show, in Atlanta, on 14 April 2016.
Prince's recording is more ornate than Sinead O'Connor's stripped-down version, and features a heavy guitar riff and a saxophone solo by frequent collaborator Eric Leeds.
But the backing vocals, recorded by the star's on-off girlfriend Susannah Melvoin, are a revelation, providing a harmonic counterpoint to the desolate lyrics.
Melvoin later recorded the first released version of the song with The Family, a band Prince put together in 1984 as a showcase for singer Paul Peterson.
"I'm so blessed and honoured to have been singing background vocals on this," tweeted the singer after Prince's demo was given its first official release on Thursday. "So much love for him."
Prince's version was recorded at the Flying Cloud Drive "Warehouse" in Eden Prairie, Minnesota - the huge rehearsal space he used before building Paisley Park - on 15 July 1984.
It was recently unearthed by Michael Howe, the official vault archivist for the Prince estate.
"I spotted the two-inch multitrack reel in the Vault some weeks back while doing a 1984-era inventory," he said in a press release. "After retrieving my jaw from the floor, we took the reel upstairs, analysed it... and digitised it.
"Even our 'faders up' rough mix was compelling enough to indicate that this was something very special indeed."
Prince's recording engineer Susan Rogers was present for the original recording in 1984.
The star was on "a creative roll, cranking out a song a day", after wrapping up his exhaustive, 98-date Purple Rain tour, she recalled.
One day, he left the studio holding a notebook and, within an hour, emerged with the lyrics to Nothing Compares 2 U.
"The song came out like a sneeze," she said, with Prince recording all of the instruments, one at a time, in his usual manner.
Rogers felt the song was "exceptional, in his top 10", but Prince didn't want to release it himself.
She theorised that the song was about his housekeeper, Sandy Scipioni, who had been forced to leave suddenly when her father died of a heart attack
"The line 'all the flowers that you planted in my back yard went out and died'… it would have been Sandy who planted those flowers," she said.
"There was no romantic relationship with Sandy. It's not a pained, 'Help me, baby' track. It's, 'You're gone and I miss you', which is probably why he felt comfortable giving the song away.
"He released his material based on what he wanted us to know about him and, wonderful as it is, he didn't want it to represent him."
The official release of the song is accompanied by a video of Prince rehearsing with his band, The Revolution, in 1984.
It became available two days before the second anniversary of Prince's death, at the age of 57, from an overdose of the painkiller fentanyl, an opioid many times more powerful than heroin, on 21 April 2016.
Prosecutors announced on Thursday that no criminal charges would be brought in relation to his death.
The attorney of Carver County, Mark Metz, said evidence showed Prince thought he was taking the prescription drug Vicodin, when in fact he was taking a counterfeit Vicodin pill laced with fentanyl.
"In all likelihood, Prince had no idea he was taking a counterfeit pill that could kill him," Mr Metz told reporters.
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