What might emerge from Prince's vault of unreleased music?

Should we get ready for a Purple Flood?

Only Prince knows what music he might release under a new agreement with his old label, Warner Bros., that also gives him control of the much-coveted master recordings of his first 19 albums. The only certainties are a deluxe edition of his bestseller "Purple Rain," which marks its 30th anniversary this summer, and an album of new material with 3rdEyeGirl.

What else might emerge from Prince's long-touted vault of unreleased music? Album projects that were abandoned? Outtakes? Demo recordings? Live albums?

The Rock Hall of Famer was a notoriously hyperproductive musicmaker in his Warners years, from 1978 to about 1996.

"We used to record two songs a day," said David Z, Prince's main engineer from 1976 until 1994.

Whatever rarities are released, they belong to Prince, not the label.

"We exhausted the Warner Bros. vault years ago," said Gregg Geller, former Warners vice president of A&R. He put together 1993's "The Hits/The B Sides," which included a handful of unreleased tunes that Prince delivered expressly for the boxed set. "One problem Prince had was productivity. He created an avalanche of music that kept coming for years. Record companies don't move that quickly."

But Prince never submitted finished material to Warners unless he was ready to release it. The exception was 1987's "The Black Album," which he pulled the plug on. The label eventually issued it in 1994.

Prince's vision seemed to be at odds with Warners' strategies.

"He did great stuff [but] he'd say: 'That's what they want from me. I don't want to put it out,' " David Z said. "He wanted to be more obscure, I guess."

A year or so after signing a reported $100 million deal with the label in '92, he started writing "slave" on his cheek and protesting his lack of ownership of his master recordings. He and Warners eventually divorced.

The new deal could mean considerably more money for Prince. In 2013, his Warners catalog sold 286,000 units, according to Nielsen SoundScan. If Prince had owned his catalog, Billboard magazine estimates his take would have been $1.7 million instead of the estimated $657,000 in royalties he likely received.

A deluxe version of the Oscar- and Grammy-winning "Purple Rain" not only promises improved sound but bonus material that could include the August 1983 concert at First Avenue when the film's songs were introduced.

"It would be a great live album," said David Z, who oversaw the recording that night. "It was the first time Wendy [Melvoin, guitarist] joined him. People had never heard the songs and didn't react because none of it was familiar. There are a few songs that weren't used in the movie or album."

Among the outtakes are an instrumental written by Prince's father, John Nelson, and a song by Jill Jones, a singer in the movie. But there were no demos for "Purple Rain," David Z said. Prince didn't operate that way with his band.

When writing for other acts, however, he'd often record a version featuring his own vocals as a guide. So there are recordings of the Time's first two albums with Prince singing instead of Morris Day. Ditto for albums by Sheila E, Vanity 6, Apollonia 6 and the Family.

Post-"Purple Rain," Prince was extraordinarily productive, creating unreleased albums known as "Camille" (rumored to be done in a high, manipulated, female-like voice), "Dream Factory" and "Crystal Ball." Some songs ended up on 1987's "Sign o' the Times," and a three-disc "Crystal Ball" was offered in 1998. But hardcore fans want the originals.

Alan Leeds, who was Prince's tour manager in the mid-1980s and later ran Paisley Park Records, said there are compelling funk instrumentals with drummer Sheila E, guitarist Wendy Melvoin, keyboardist Lisa Coleman and saxophonist Eric Leeds (Alan's brother).

David Z remembers a Prince blues album by a three-piece band. There were rumors of a rock power trio with drummer Michael Bland and bassist Sonny Thompson. Prince's jam sessions with legendary jazz trumpeter Miles Davis yielded only one released song (on a Chaka Khan album), but are there more? What about the three numbers he wrote and recorded for Bonnie Raitt pre-"Nick of Time," or the tunes he wrote with Kim Basinger during their "Batman" fling? And who wouldn't want to hear his version of "Manic Monday"?

Whatever's on your wish list, let's hope Prince opens the Purple floodgates.

Twitter: @JonBream • 612-673-1719