At an age when many famous rockers would be cashing in through nostalgia tours, David Bowie has instead set off on a new phase of a career already defined by invention.

The rock icon marks his 69th birthday on Friday by releasing "Blackstar," which is his 25th studio album and one of his most innovative yet as Bowie subtly but doggedly breaks free from traditional pop structure.

The new Bowie sound is rooted in jazz, but a hard jazz, as an accelerating tenor saxophone and heavy rhythm section chase his vocals maze-like throughout the songs.

Bowie created "Blackstar" by teaming up with the quartet of saxophonist Donny McCaslin, who has probed the reaches of modern jazz through driving funk and electronic backdrops.

McCaslin's saxophone carries much of the album, yet other instrumentation creates a sense of dread and tension, from the dark bass that opens "Lazarus" to the morose piano chords that begin the elaborate "Dollar Days."

Yet the title track, which starts off the "Blackstar" album, runs for nearly 10 minutes and is guided firmly by Bowie's voice. He sings in a gentle wail in cryptic verses about death and religion.

"On the day of execution / Only women kneel and smile," sings Bowie, in imagery reinforced by a nightmarish video in which he appears blindfolded with beady eyes.

James Murphy, the force behind LCD Soundsystem, one of the most influential electronic bands of the 2000s, contributes percussion on two tracks.

- Change a constant for Bowie -

"Blackstar" is the second album since Bowie's re-emergence in 2013. That year, he released "The Next Day," his first album in a decade, which he announced on his birthday to stunned fans who presumed he had retired.

But Bowie is finished with live performances, according to a report last year that quoted his agent.

If true, the final concert by the performer who pioneered theatrical glam rock would have been a set of just three songs at a charity show in New York in 2006.

Yet the British artist, who is a longtime resident of New York, has stayed active on side projects. He composed the music for the current off-Broadway play "Lazarus," based on the science fiction novel "The Man Who Fell to Earth" whose 1976 film version starred Bowie as an actor.

Bowie rarely speaks in public. But his longtime producer Tony Visconti said that Bowie always had a "hint of jazz" in his work.

Visconti, speaking to National Public Radio, said the unwritten concept of "Blackstar" was to find jazz musicians who "weren't necessarily going to play jazz."

"If we used rock musicians trying to play jazz, it would have been a very different album," he said.

While full-on jazz is new for Bowie, experimentation is in some ways the norm for the singer whose early hits included "Changes" and whose song "Golden Years" is now 40 years old.

Bowie's most celebrated venture into new musical territory came in his "Berlin Trilogy" albums in the late 1970s when he also played with form and turned to abstract electronic sounds inspired by the scene in his temporary home of Germany.

Bowie is also no stranger to saxophone, which he plays himself and notably included on his hard-charging "Tin Machine II" album released in 1991.

- Modern takes on past -

Despite the large musical ambitions of "Blackstar," Bowie keeps the album succinct at seven tracks.

He originally composed the title track for the French-British crime television series "The Last Panthers."

Another song, "'Tis a Pity She Was a Whore," is a gender-bending, modernist take on the horror of World War I.

Bowie again reaches back lyrically in "Girl Loves Me" which he sings mostly in Polari, the slang used by Victorian London's gay underground.

Bowie turns wistful, if still abstract, on the album's final songs as keyboards converge into a dreamlike aura.

"Seeing more and feeling less / Saying no but meaning less / This is all I ever meant," Bowie sings, concluding aptly: "I can't give everything away."