David Bowie in 1987. (AFP/Getty Images)

He has flown under the radar for decades now, his name popping up every time David Bowie was about to make a big move. A new tour, a financial endeavor — even when Bowie first set up his email account, Bill Zysblat was there. Now, the longtime business manager will be responsible for the music and money of David Bowie in the afterlife.

Nearly three weeks after Bowie's death from cancer this month, his final will was filed in New York. The 20-page document, prepared in 2004, named Zysblat and lawyer Paddy Grafton Green as the chief executors of his estate. According to the New York Times, the will was amended to indicate that Green was no longer an executor, leaving Zysblat in charge.

Per the will's directions, Zysblat will divide up Bowie's assets: 50 percent to his wife, supermodel Iman Abdulmajid Jones; 25 percent to their daughter, 15-year-old Alexandria, or "Lexi"; and 25 percent to his son from a previous marriage, 44-year-old film director Duncan Jones. Bowie also left $2 million to Corinne "Coco" Schwab, his longtime personal assistant who many believe to be the subject of his song, "Never Let Me Down," and $1 million more was gifted to his son's former nanny, Marion Skene.

According to the will, Bowie was worth $100 million when he died. But immensely popular artists don't cease making money when they're no longer around to sing. Bowie's worth will continue to grow as "Blackstar," the album released just before his passing, keeps selling. The record was Bowie's first to reach No. 1 on the Billboard charts. The following week it dropped to No. 4, behind albums from Panic! at the Disco, Adele and Justin Bieber.

"Blackstar" won't be the last of Bowie's music, though. His producer, Tony Visconti, told Rolling Stone that Bowie had written and recorded at least five songs yet to be released. Newsweek reported that there is a "long list of unscheduled musical releases that Bowie planned before he died."

Zysblat is likely to be one of the chief decision-makers on when and how to release that music, a key step in keeping the Bowie legacy alive. Posthumous business has the potential to be a huge money-maker for artists' estates, but it always risks being perceived as tacky or exploitative. Naturally, someone who has worked extensively with an artist is more informed about what the artist would have wanted his post-death career to look like.

[How death brought David Bowie a career breakthrough]

That was the case for the Michael Jackson estate. The co-executors, who worked with Jackson before he died, oversaw multiple posthumous albums, live shows, books and documentaries. Since Jackson's 2009 death, they've made $1 billion, according to estimates by Forbes.

Though little is known about Zysblat's personal relationship with Bowie, he is known professionally as Bowie's financial sage. Bowie biographer Paul Trynka said Zysblat first joined Bowie as an accountant for the 1983 tour promoting the breakthrough hit, "Let's Dance." Zysblat had previously worked with the Rolling Stones.

By the 1990s, Zysblat was a key adviser to Bowie, who, unlike many artists, managed himself. Zysblat is always included in the story of "Bowie bonds," when Bowie sold off the rights to his future earnings on Wall Street for $55 million. Bowie was the first musician to take such a risk with the royalties from his already-released albums. Soon after, other artists were coming to Zysblat and his financial partner, Joe Rascoff, to get in on the same deal.

Search for Zysblat online today, and you'll find little more than the times he was quoted talking about his clients or the music business. His company with Rascoff, RZO, has been known to work with Patti LaBelle, Patti Smith, Sting, the Police and U2. He was a producer on "Moon," the science fiction film by Bowie's son.

RZO's website says it is under construction, but screenshots captured by Archive.org indicate the site has been in that status since 2009.

Zysblat stays out of the spotlight, and that's just the way that artists today like it, said Trynka, who wrote "Starman: David Bowie."

"He's not flamboyant. He seems to be very well liked, he's good with the numbers, and he's reliable."

More about David Bowie's life and legacy: 

This is how David Bowie confronted MTV when it was still ignoring black artists

Beyond the music: How David Bowie was one of our smartest visual artists

The many looks of David Bowie, rock's greatest fashion visionary