MTV, which arrived in 1981, was part of the change. Prince was born for music video; he was not just a consummate musician but also a dancer and dresser who knew exactly how to play to a camera. MTV started with its own race problem, trying at first to present itself as the visual equivalent of an FM rock radio station, with an overwhelmingly white playlist. That was foolish or worse, and on the “1999” album, Prince’s “Little Red Corvette” called the bluff of MTV’s format; after all, it was a song about classic rock topics, a car and a girl, complete with electric guitar. The video — with Prince’s bedroom eyes, glittery purple trench coat and a sudden burst of dancing — made clear that he could not be contained.

But commercial triumph wasn’t the sole measure of “1999.” Prince was expanding his musical ambitions, writing odd-angled melodies (like “Let’s Pretend We’re Married”) and toying with ambiguous harmonies, as in “Something in the Water (Does Not Compute).” Even as he was establishing himself as a sex symbol, he was placing his come-ons alongside confessions of insecurity, like “Irresistible Bitch” (the B side of “Let’s Pretend We’re Married”) and “Little Red Corvette” itself. He presented himself as the seducer or the seduced, not a conqueror; “Teacher, Teacher,” another newly released vault song, has him fending off a lonely teacher’s unwanted advances.

Prince was also finding new sounds: pushing his voice into multiple personalities, from sweet falsetto to punk snarl to preacherly exhortation, and deploying sounds from the latest synthesizers. He had one of the first drum machines, the Linn LM-1, which made it possible to program realistic sampled sounds quickly. (One reason “1999” sounds current is that many pop songs are still driven by brittle, metronomic drum-machine beats.) Prince’s production brought his inventiveness to acoustic instruments as well, like the way the quasi-fanfare that introduces the song “1999” shimmers expectantly with a flurry of cymbals.

Image The “1999” reissue comes in a host of configurations; the super deluxe version includes previously unreleased music from his vault.

The vault material reflects Prince’s remarkable early 1980s multitasking, pouring out material not only for his own albums but also for groups he was producing: the Time and Vanity 6. He often wrote and recorded a song in a day. Crisp funk workouts like “Feel U Up” and “Rearrange,” from the vault, could have easily ended up on a Time album, though Prince didn’t treat them like demos. He finished the tracks with a flourish; “Rearrange” turns into a feedback-slinging lead guitar freakout.

Other songs put Prince’s stamp on all sorts of idioms: romping through synthesizer equivalents of garage-rock (“Yah You Know”) and rockabilly (“No Call U”) and infusing synth-pop with lascivious glee in “Turn It Up,” which urges someone to “Work me like a radio” and “Come and play with my controls.” (For Prince, every machine was a sex machine.) “Vagina” celebrates a character he meets who is “Half-boy, half-girl — the best of both worlds,” while Prince makes two guitars and a bass — recorded one by one — sound like the Rolling Stones jamming in a dressing room.