Issued without advance notice 17 days after Kendrick Lamar's riveting 2016 Grammy Awards performance, untitled unmastered.

consists of eight demos that are simply numbered and dated.

Apart from segments previewed at the Grammys and late-night television appearances, there was no formal promotion.

A postscript, it's (artfully) artless in presentation -- not even basic credits appear on the Army green liner card in the compact disc edition -- yet it's almost as lyrically and musically rich as To Pimp a Butterfly.

The dates indicate that the majority of the material was made during the sessions for that album, and the presence of many of its players and vocalists is unmistakable.

This was assembled with a high level of care that is immediately evident, its components sequenced to foster an easy listen.

Track-to-track flow, however, is about the only aspect of this release that can be called smooth.

After an intimate spoken intro from Bilal, the set segues into an urgent judgment-day scenario with squealing strings and a resounding bassline as Lamar confronts mortality and extinction with urgent exasperation.

He observes terrifying scenes all the while sensing possible relief ("No more running from world wars," "No more discriminating the poor").

untitled unmastered.

offers this and other variations on the connected themes of societal ills, faith, and survival that drove the output it follows, with Lamar at his best when countering proudly materialistic boasts with ever-striking acknowledgments of the odds perilously weighted against his people.

Remarkably, this hits its stride in the second half.

The stretch involves a rolling, ornamented retro-contemporary production from Adrian Younge and Ali Shaheed Muhammad (with vocal assists from Bilal and Cee Lo Green), a stitched suite that is alternately stern and humorously off the cuff (featuring Egypt, five-year-old son of Alicia Keys and Swizz Beatz, as co-producer and vocalist), and a finale of Thundercat-propelled funk.

Even while coasting over the latter's breezy and smacking groove, Lamar fills the space with meaning, detailing a confrontation with sharp quips and stinging reprimands.

While Lamar referred to these tracks as demos, and not one of them has the pop-soul appeal of "These Walls" or the Black Lives Matter protest-anthem potential of "Alright," untitled unmastered.

is no mere offcut dump.

It's as vital as anything else its maker has released.