Prince's Sign "O" The Times is arguably the iconoclast's most ambitious project. The double album trailed the commercial breakthroughs 1999 and Purple Rain while marking his first release since 1986's Parade, his final project with the Revolution.  

Lyrically, there are social commentaries on AIDS, crack and machine guns in the title track, religious references via "The Cross" and romantic sentiments expressed in "Adore" and "If I Was Your Girlfriend." Musically, Sign "O" The Times comprises a collage of familiar Prince-like R&B/funk workouts, high-octane rock, slow burns, and sexy jams — all enveloped by virtuoso eclecticism and then-cutting-edge production.

It's unmistakably Prince, yet he somehow manages to preserve an air of unpredictability throughout the sprawling song cycle, which Rolling Stone's original 1987 review described as "tough and inventive and exuberantly experimental."

With Sign "O" The Times turning 30 on March 31, here are nine lesser-known facts about what some fans consider Prince's finest hour-plus of music.

Sign "O" The Times resulted from three aborted projects 

The album's eclectic roots go back to a genre-bending triple LP project Prince envisaged in 1985 under the working title Crystal Ball. Prince later abandoned that project, which featured tracks such as "The Ballad Of Dorothy Parker" and "Starfish And Coffee," and began work on Dream Factory, a work anchored by a new sped-up vocal style. Though Dream Factory featured tracks such as "I Could Never Take the Place Of Your Man," it was shuttered and Prince segued into work on Camille, a pseudonym-based project titled after his androgynous feminine vocal alter ego. Ultimately, Prince wanted to compile a new triple album with tracks from the three aborted projects but his label balked at the idea. Prince relented and pieced together a double album, which was titled Sign "O" The Times.

You can play the instrument Prince used on the title track on your phone

For the title track, Prince incorporated a guitar, Linn machine and Fairlight Computer Musical Instrument, a digital sampler and screen-based rhythm sequencer. Rather than programming new sounds, however, Prince reportedly used one of the Fairlight's stock presets. Today, Apple users can download a CMI app and play it like Prince on their iPhone or iPad.

The video for "Sign 'O' The Times" is cited as the first lyric video

Nowadays, lyric videos are commonplace. But in 1987, Prince turned in what is widely considered as the first-ever lyric video with his visual treatment for the album's title track, which was directed by Bill Konersman. While Bob Dylan utilized flash cards for select words in his video of 1965's "Subterranean Homesick Blues," Prince featured all of the song's lyrics onscreen while opting to not appear in the video.

"Why he chose to just show the lyrics when nobody had ever done so as starkly as this, was just an aspect of his creativity," Konersman tells GRAMMY.com. "At the time, I was a Macintosh-literate graphic designer [and] my sister was a video producer, and her husband was Prince's main photographer. And there was no time to find a 'real' director with any better knowledge of digital graphics or typography. The graphics are lamentably crude. Times Roman was the only font they had, and they had made it themselves by tracking with a mouse [and] a blown-up Photostat from a type book …this was before true 3-D graphics."

Revisit Prince's GRAMMY memories

The vocal effect on "If I Was Your Girlfriend" was an accident

From vocal alter-egos to his soulful croon on "Adore" and the distorted textures of "If I Was Your Girlfriend," Prince experimented with a variety of vocal styles and sounds on the album. However, the latter song's vocal effect was unintentional, according to engineer Susan Rogers. "Prince wanted to do his vocals alone as usual, so I set him up with his mic and left the room," said Rogers in the 1998 book, Slave To The Rhythm. "I just inadvertently had something switched the wrong way that day and when I came back in and heard the finished vocal, I thought, 'Oh no!' It was so distorted. I thought, 'He's going to kill me.' He never said a word. He had the attitude, 'Well, maybe that was meant to be.'"

"The Ballad Of Dorothy Parker" isn't really about Dorothy Parker

Yes, the laid-back tune namechecks the noted 20th-century poet/satirist Parker, but the lyrics center around a sharp-tongued waitress who serves up clever quips such as "Sounds like a real man to me." "It turned out he didn't have any clue [who Dorothy Parker was]; he just picked the name because of how it sounded," saxophonist Eric Leeds told Mojo. A huge Joni Mitchell fan, Prince worked in a Mitchell reference to the song with the lyric "And it was Joni singing, 'Help me I think I'm falling,'" which is a tip of the cap to her 1974 track "Help Me."

The album spawned covers and samples by 2Pac, Billy Cobham, Nina Simone, and TLC

Fittingly, various songs on the album have been reinterpreted by a variety of artists spanning multiple genres. Jazz fusion drummer Billy Cobham turned in an instrumental version of the title track for his 1987 album, Picture This. Simone recorded the song for her final studio album, 1993's A Single Woman, though it was only released as an outtake on a later expanded album version. 2Pac incorporated a live sample of "If I Was Your Girlfriend" for his song "Thugs Get Lonely Too"; TLC covered the song on 1994's CrazySexyCool. Electronic artist Gary Numan covered "U Got The Look" for his 1992 album, Machine + Soul.

Prince's "Sign 'O' The Times" vinyl single among 2017 Record Store Day exclusives

The album features lifts from Mendelssohn and The Wizard Of Oz

A brief, if random, sample of Felix Mendelssohn's "Wedding March" is incorporated in the intro of "If I Was Your Girlfriend." And yes, that's the Wicked Witch's chant ("Oh-wee-oh") from The Wizard Of Oz worked into the album's funky penultimate song, "It's Gonna Be A Beautiful Night," which was recorded in Paris. Other elements on the album, including the crystal ball featured on the cover, have been debated by Prince fans as being additional references to the iconic 1939 film.

Sign "O" The Times nearly matched a high-water chart mark for Prince

Sign "O" The Times spawned three Top 10 singles with the title track (No. 3), "U Got The Look" (No. 2) and "I Could Never Take The Place Of Your Man" (No. 10). Prince's only other album to birth more Top 10 hits was the Purple Rain soundtrack, credited to Prince & The Revolution, which featured "When Doves Cry," "Let's Go Crazy," "Purple Rain" and "I Would Die 4 U."

The album netted three GRAMMY nominations and GRAMMY Hall Of Fame induction

Though the album did not garner a GRAMMY, Prince received three nominations, including an Album Of The Year nod for Sign "O" The Times. (The award ultimately went to U2's The Joshua Tree.) "U Got The Look" received Best Rhythm & Blues Song and Best R&B Performance By A Duo Or Group With Vocal nominations. In 2017 Sign "O" The Times became Prince's third album to be inducted into the GRAMMY Hall Of Fame.

Want more Prince? Watch his final appearance on the GRAMMYs