For all the times David Bowie changed his getup—the glam alien of Ziggy Stardust, the moody existentialist of the late ’70s, the pop sophisticate of the ’80s, and so on—he was a remarkably consistent barometer of where the culture was headed, from gender fluidity to the hybridization of rock and electronic music. The London native first released music under his given name, David Jones, before donning the Bowie alias and finally conveying his dreamy sense of dislocation with 1969’s “Space Oddity.” Themes of alienation came naturally to him, as heard on several uncanny singles he released between 1972 and ’73: “Changes,” “Starman,” and “Life on Mars?” Bowie’s visual and sonic identity continued to rapidly morph after that, from the punky rabble-rouser of 1974’s “Rebel Rebel” to the Philly-soul Svengali of “Young Americans” the following year. Even the stubborn experimentation of his “Berlin Trilogy” of albums yielded 1977’s saturated future-standard ““Heroes”,” before 1981’s Queen teamup “Under Pressure” ushered in a new decade with breathless urgency. It also foreshadowed the consummate collaborator who would team up with everyone from Nile Rodgers (1983’s “Let’s Dance”) and Mick Jagger (1985’s “Dancing in the Street”) to Pet Shop Boys (1996’s “Hallo Spaceboy”), and Brian Eno (1997’s “I’m Afraid of Americans”). Whether holding court over drum ’n’ bass and industrial backdrops or enveloping himself in diffuse art-rock (2013’s “Where Are We Now?”) and brooding jazz (2015’s “Lazarus”), Bowie always knew to never stand still as a creative entity. That lends his half-century songbook a lingering quality of flux, as if it’s still mutating before our eyes.