“Eureka!” Although the word tends to be followed by an exclamation point to communicate the enthusiastic rush of discovery, director Nicolas Roeg had a more sarcastic tone in mind when he titled his 1983 film. Eureka stars Gene Hackman as Jack McCann, a prospector who strikes it rich after 15 years of toil and seems to be set for life. He even buys his own Caribbean island, where he takes up residence amidst unimaginable wealth. But to paraphrase the late Christopher Wallace, more money begets more problems for McCann; his fortune turns out to be an albatross that turns both mobsters and his own family against him. I’ve never seen the movie, but plot synopses suggest its outlook on life is less than optimistic.

No wonder, then, that Jim O’Rourke decided to name an album after Roeg’s movie. This is the guy who two years later would sing, “If I seem a bit remote/ You’ll feel better if you say I’m a misanthrope/ Or whatever floats your boat/ As for me, I’d rather sink my own.” When he deigns to open his mouth on a record, what comes out is almost always cynical. That sardonic disposition is one of the constants of O’Rourke’s pop-minded songwriting, be it under his own name or with Jeff Tweedy and Glenn Kotche as Loose Fur. It’s all over Eureka, and not just in the discomfiting cartoon cover art. “Do you feel pride about being alive?” O’Rourke asks mockingly. “Does the mirror say, ‘Good day, today’?” Elsewhere he declares, “Nothing makes me want to disappear as when someone opens their mouth.” His last words on the album: “I only came to leave.”

Yet like most records O’Rourke’s had a hand in, Eureka — released 20 years ago today — really is an epiphany. And like so many of those projects, it demonstrates how deep his communal bonds truly run. O’Rourke, a Chicago native, spent the decade leading up to Eureka tied into the city’s vibrant experimental music scene, an interconnected web of artists spinning wildly exploratory sounds in the realms of rock, post-rock, jazz, folk, and more. Beyond his own bands such as Gastr Del Sol and Brise-Glase, he has credits on a mind-boggling number of classic albums by both indie household names and genuine obscurities. You don’t maintain long-term working relationships with dozens of acclaimed musicians without being at least a little bit social.

Many of those people contributed to Eureka. Kotche appears several times to reorder time and space with his drumming the way he would on so many of Tweedy’s songs upon joining Wilco a few years later. The instrumental “Through The Night Softly” features Drag City co-founder Rian Murphy on drums alongside sax work by Ken Vandermark, who was awarded a MacArthur Fellowship for his endlessly curious jazz dalliances the same year Eureka came out. Several members of his Vandermark 5 can also be heard as well, including cellist Fred Lonberg-Holm and trombonist Jeb Bishop, who also played with Vandermark in the early days of free-jazz noise freaks the Flying Luttenbachers. Bishop’s trombone often combines with cornet by Chicago Underground Collective’s Rob Mazurek and trumpet by Shellac’s Bob Weston. O’Rourke’s Brise-Glase bandmate Darin Gray plays bass on three tracks. Psychedelic country singer Edith Frost throws knowingly hokey retro backing vocals on a cover of Burt Bacharach’s “Something Big.”

You read that right: Eureka features a Bacharach cover, one that lays on the cheese so thick you can practically see the jazz hands. And that’s not the only moment on the album that could be described as pop. O’Rourke had assembled this battalion of avant-garde geniuses in service of his most accessible album to date. At Bandcamp, where you’re instructed to “please download the best possible quality” — by the way, purchasing it is still the only way to hear it legally — Eureka is playfully dubbed an “experimental MOR album.” But its spectacular shapeshifting sprawl is only MOR by O’Rourke’s esoteric standards.

We begin with “Prelude To 110 Or 220/Women Of The World.” The expansive Ivor Cutler and Linda Hirst cover quickly blows out the Fahey-inspired guitar instrumentals of O’Rourke’s 1997 release Bad Timing into a small-scale orchestra that sounds like millions of fireflies dancing. O’Rourke’s droll, conversational voice soon enters with the song’s only lyrics, as close as the album gets to a positive sentiment: “Women of the world take over/ ‘Cause if you don’t, the world will come to an end/ And it won’t take long.” That refrain, a kick drum heartbeat, a pulsing fingerstyle acoustic riff, a brilliant swirl of atmospheric melody: all of it keeps cycling, building, intensifying, until you’re swept up into Eureka’s immaculate chamber-pop headspace.

From there the album is as restlessly adventurous as you’d expect from O’Rourke, applying his signature touches (nimble melodies, complex arrangements, unconventional structures) to a range of soft-rock sounds. “Ghost Ship In A Storm,” a lounge-ready jazz-pop number marked by strikingly pretty piano flourishes, soundtracks O’Rourke’s lament about riding his bike into wet cement while wondering if he paid his rent; eventually it bottoms out into shapeless French horn reverie, then reemerges with weeping pedal steel and quietly vibrant house piano. The sound of shakers like crickets on a summer night carries us into the shadowy, atmospheric first half of “Movie On The Way Down,” which gives way to snide keyboard balladry dressed in rumpled symphonic beauty.

The gorgeous transformations continue throughout the tracklist: wistful piano colored first by woodwinds and later some light organ; a sassy brass breakdown out of a Saturday Night Live house band fever dream; jazz segments both blustery and stately; snappy, campy bossa nova; a watery guitar slow-drift that spills over into ornate orchestral drama; a strummy electric guitar farewell that bursts into falsetto dissipation. It’s all of a piece, but the scope of styles is breathtaking, even as O’Rourke’s lyrics turn it all into a sick joke. “As things stay the same, I’m quickly running out of change,” he remarks on the title track, yet this music only builds currency as the years go by. Besides aging marvelously on its own terms, you can hear Eureka echoed in a number of other landmark releases, be it the dreamlike splendor of Wilco’s O’Rourke-produced A Ghost Is Born or the folksy post-rock symphonies of Sufjan Stevens’ Michigan and Illinois.

But no one does this sound like O’Rourke himself, and even he wouldn’t keep it up for long. After pushing it further into the classic rock realm on a pair of even more approachable sister releases, 1999’s Halfway To A Threeway EP and 2001’s incredible Insignificance, he spent most of this century producing other artists and releasing more experimental works, highlighted by 2009’s instrumental The Visitor and the vast collection of Steamroom releases he’s been compiling since 2013. A pair of Loose Fur albums in 2003 and 2006 offered brief glimpses of O’Rourke’s pop side, but the aesthetic has been scarce enough that when he finally returned to it for 2015’s Simple Songs, it was a eureka moment in every sense of the word — one entirely worthy of an exclamation point.