A decade and a half ago, DJ Shadow stopped the clocks at midnight. Had he kept the timepieces frozen for an entire career, it's unlikely that anyone would've complained. After all, his debut, "Endtroducing," was a timeless record that defined trip-hop's American variant and established a foothold for the genre of instrumental beat music.

Ask anyone from the Low End Theory crew to the dubstep spawn of Hyperdub and Hemlock Records, and it's likely that Shadow will be name-dropped as a primary influence. With his legacy long secured, Shadow could essentially tweak his old formula and conjure something that would neatly parallel the contemporary zeitgeist.

But through his lengthy delays between albums, his collaborations with Cut Chemist and his flirtations with hyphy on 2006's "The Outsider," the man born Joshua Davis has never retraced his footsteps. His latest two tracks (available for streaming only for the next 24 hours) bear his creative restlessness.

Intended for release on a yet untitled album due sometime next year, "Def Surrounds Us" is an eight-minute fire alarm of frantic ideas. A scratched vocal chants "def surrounds us" (or "death surrounds us," depending on how your ears hear it). Consisting of several mini-suites, it opens like an early British grime track before descending into subterranean bass lines and Benedictine-style chants. By its midpoint, it sounds like a house-inflected Kode9 or Actress production that could fit nicely into the contemporary bass music world. It then suddenly settles into a coda of a pretty piano lilt.

As the man from UNKLE -- the shape-shifting sound system responsible for some of the most forbodingly cerebral, beat-driven tunage of the last dozen years -- James Lavelle has demonstrated a knack for picking collaborators who can help enable his singular goal. That is, exploding the boundaries of electronic music in pursuit of an ideal that transcends the dance floor and careens into darker terrain.

Creating the right marriage of sensibilities for such a project requires a rare skill. It’s one mitigated only by the tastemaking producer’s secondary tendency: to drive a stake between himself and his collaborators almost the minute a new CD hits retail -- and sometimes well before.

But now, after a three-year recording hiatus, Lavelle, 36, is back with a new partnership; his old pal Pablo Clements now rounds out the official UNKLE roster. And there’s a well-reviewed new CD, “Where Did the Night Fall,” which came out Tuesday.

It features collabos with the likes of Angeleno shoegazer band Autolux, Texas psych-rockers the Black Angels and ex-Screaming Trees and Queens of the Stone Age vocalist Mark Lanegan. In a review this month, BBC Music described “Where Did the Night Fall” as “electronic psychedelic groove flushed with drama. Neither space rock nor alt-dance but flickering somewhere on the cusp of both,” also hailing the fifth UNKLE album as “a stirring, seductive minor classic.”

What could be better than dancing to DJ Shadow, spinning live from a crate of vinyl in a small ballroom at L.A.’s Park Plaza Hotel with an almost-full moon pouring through the patio windows? Doing it with that room full of people in outrageous Halloween costumes.

L.A. came out swinging for Masquerade, KCRW’s Halloween Ball, filling the neo-Gothic Park Plaza with thousands of epic costumes such as matching luminous jellyfish, a giant blue “Yip-Yip” from “Sesame Street,” a human marionette, an iPhone and a “missing” face on a milk carton -- all of it proof that we live in a town full of prop shop folks. 

Of course, there were also miles of sexy Spartans and schoolgirls and Bo-Peeps and whatever else you were looking for. 

The five opulent and differently themed rooms were hot (despite the cool evening) and nearly packed, and Shadow had his fans jumping up and down from the very first wild outburst of scratching. Minutes in, he laid into an inspired mix of “Bustin’ Loose” from Chuck Brown and the Soul Searchers entwined with the Zombie’s version of “Time of the Season,” with the phrase “Who’s your daddy” hiccuping out every few bars. 

“Y’all ain’t ready for this next one,” Shadow dropped enigmatically, saying his next piece was “where Kanye West meets Metallica.” It wasn’t nearly as well received, but like he said, we obviously just weren’t ready.

Upstairs in the Terrace Room, KCRW’s Liza “Diva of Death” Richardson held it down in a gorgeous white tangle of corsets and what she called “rehearsal skirts” for doing Shakespeare and Moliere, topped with creepalicious face paint, as she turned over a good-size crowd to a live performance by Sea Wolf. 

The L.A. musical landscape is thick with options over the rapidly approaching Halloween weekend.

Beat-crazy dance aficionados can choose between the 12th annual Monster Massive at the L.A. Sports Arena and the expanded two-day HARD Haunted Mansion event at the Shrine. Indie rockers can check out stalwarts Built to Spill at the Echoplex and/or new heroes the Dirty Projectors at the Jensen Rec Center.

Public radio powerhouse KCRW has entered the Halloween party fray with “Masquerade,” a costume ball and dance party at the Park Plaza Hotel in downtown L.A. that now boasts Bay area legend DJ Shadow as the headliner.

DJ Shadow joins a lineup that already includes Swedish indie urban rock outfit Little Dragon alongside such local acts as mod folkie Sea Wolf and sunshine-poppers Edward Sharpe and  the Magnetic Zeros. A who’s who of KCRW DJs, including Liza Richardson, Jason Bentley and Garth Trinidad, will spin at the event too.

Tickets are available at KCRW.tix.com

-- Scott T. Sterling

Photo: DJ Shadow performing at the Mayan Theater. Credit: Lawrence K. Ho / Los Angeles Times.