Mourning David Bowie requires tremendous energy because there are so many David Bowies to mourn. The lost cosmonaut. The alien balladeer. The pansexual glamourpuss. The rake. The maestro. The fashionista. The freak. He was humanity’s ultimate and most giving rock star. A chameleon bearing gifts.

For five decades, Bowie — who died Sunday at age 69 — reimagined himself over and over again, colorfully implying that music should change while quietly insisting that human beings can change. In that sense, Bowie’s mutations were a manifestation of his generosity. Being yourself is fine, but being every iteration of yourself is living. Renewal is possible. Still. Always.

He made sure that we learned that big lesson with our eyes as well as our ears. As rock’s greatest shape-shifter, Bowie always had fresh ideas about love, alienation, pleasure and progress churning beneath each new haircut. With an imagination deeper than his wardrobe, he was an omni-star, casually drifting across a vast terrain at high speeds.

“As far as I’m concerned, the whole idea of Western life, that’s the life we live now, is wrong,” he told Melody Maker near the dawn of his career at the age of 19. “The majority of us just don’t know what real life is.”

So as a rebuke, he set off to live the largest life possible, pushing toward the edges of his creativity, his sexuality and his humanity. In 1971, he sang about that push, and the push back: “Time may change me, but I can’t trace time.” A few months later, after he told a journalist he was bisexual, the media’s overblown reaction made him instantly paranoid — but it made him an instant sensation, too.

“We wanted to manufacture a new kind of vocabulary,” Bowie told NPR in 2003, looking back on his launchpad years. “I think we took it on our shoulders the idea that we were creating the 21st century in 1971.”

That electric futurism surged through all of Bowie’s best work. He defined rock-and-roll theatricality with his 1972 glam opus, “The Rise and Fall of Ziggy Stardust and the Spiders From Mars.” In the late 1970s, he relocated to Germany and released what’s now known as his Berlin trilogy — “Low,” “Heroes” and “Lodger” — three innovative recordings that still sound like tomorrow. And in 1983, he teamed up with Nile Rodgers of Chic for “Let’s Dance,” an album whose chart-topping title track offered a perfect lyric about getting dressed-up for physical catharsis: “Put on your red shoes and dance the blues.”

By then it had become clear that perpetual rejuvenation was the beating heart of Bowie’s project, and listeners began to expect the same of anyone singing a pop song. If this guy can change, then so can we, and so should everybody else.

Bowie’s trajectory demanded that all pop stars evolve, transform, tweak their personas or invent new ones. He made reinvention one of pop music’s most essential, appealing and enduring requirements. (Today, players abuse that inheritance when they think of their artistic identity as their “brand.”)

It’s also important to remember that Bowie didn’t turn every day into Halloween. As incredible as they were, those clothes weren’t costumes. As astonishing as they were, those transformations weren’t acts of evasiveness. Through each metamorphosis Bowie put himself through, he projected himself with the purposeful curiosity of a traveler, never a tourist.

Like in 1977, when he sauntered into a famous Christmas duet with Bing Crosby, “Peace On Earth/Little Drummer Boy.” At the time, some tiresome manager-type must have pitched this as an odd-couple duet. But if you grew up hearing the song during the holidays, it sounded completely natural — just two great singers pa-rum-pum-pum-pumming. One was a former spaceman, now fully assimilated, taking his job seriously.

And while Bowie’s recording career slowed as the years wore on, he remained a true mutant for the whole ride.

Just last Friday, on his 69th birthday, he released “Blackstar,” his 25th studio album. It’s a jazz-soaked song-cycle that’s enigmatic and harsh. But as ever, it finds Bowie searching his own margins in hopes of presenting himself to the world anew.

It was to be his penultimate transformation. Two days later, he made the final one — from a singular life into a million memories.