Here's what makes Green Mill the "most authentically Chicago" venue in town

"Thank you ladies and gentlemen. Remember: No applause. And keep it down — don't rattle the ice in your glasses, and don't ring the cash register. We got it covered?"

That's how Charles Mingus memorably opens "Original Faubus Fables" from his 1961 album Charles Mingus Presents Charles Mingus. Mingus was perpetually annoyed at the lack of respect paid to live jazz performances ("Isaac Stern doesn't have to put up with this sh*t!" he once reportedly complained to a less-than-rapt audience).

I couldn't help but recall that particular instance of crowd shushing during a recent visit to the Green Mill, the legendary jazz club located on Chicago's northeast side. Some friends and I were attending to see Patricia Barber, a singer-pianist-composer with a dozen records — most of them on Blue Note — to her name. As we arrived, the bouncer reminded us, "Tonight is a quiet show, so no talking and no flash photography."

Not that most anyone who comes to the Green Mill needs such a reminder. Those who aren't immediately awed into respectful silence by the overwhelming coolness of the place either find themselves hushed by fellow patrons or swiftly removed by bouncers before their noisiness can break the spell of the music.

Patricia Barber (left) performs with her quartet at the Green Mill in September 2016.Instagram

A special place: The Green Mill is what one might call a "special place." It's a place you take visitors from out-of-town to give them a taste of the real Chicago, a place you make a point to return to when you realize it's been too long since your last visit. And if you're a committed jazz maven, it's where you find yourself most weekends, along with whomever among the world's top players is heating up the storied club's cozy stage that night.

There's a reason a musician of Barber's stature — someone who plays to international audiences on stages in Paris, Budapest and Vienna — should want to make the Green Mill her home stage.

"This is genuine Deco," she explains, motioning toward the statue of the Greek god Ceres that occupies the corner behind the piano. "Those cash registers don't any have electronics in them — there's only one guy who can fix them, and he's 99."

"It's authentic," Barber tells us. "It's the most authentically Chicago place you'll ever find."

The specialness of the Green Mill is hard to miss. It announces itself boldly with its immaculately maintained green neon sign lighting up the intersection at Lawrence and Broadway. Its fabled Prohibition-era past is evident long before you step up to the vintage, cash-only bar and take in the ornate woodwork.

Al Capone's mugshotWikimedia Commons

The weight of history: The weight of that history and preeminence has certainly helped the Green Mill maintain its status among local watering holes, even if not all the stories from the joint's sordid past are true. Established in 1907 as Pop Morse's Roadhouse, it was rechristened the Green Mill Gardens at some point in the '10s. The new name, a rejoinder to Paris' Moulin Rouge (or "red mill"), certainly spoke of grandeur, and the early clientele from the nearby Essanay film studios (including a young Charlie Chaplin) was suitably glamorous.

Like many places on the city's north side, the Green Mill's most fabled decade was the Roaring '20s, when an even bigger star than Chaplin — Al Capone — claimed occupancy of his favorite booth near the short end of the bar. The stories of the Volstead-era Green Mill — tales of secret escape tunnels and bullet holes — are the stuff of gangland legend (the story of Green Mill singer Joe E. Lewis and his failed attempt to jump to a rival club inspired the 1957 Frank Sinatra film The Joker is Wild).

But while its retro appeal and underworld mystique are enough to make the Green Mill a beloved Chicago institution, they almost obscure what gives the joint its well-earned longevity and why, in its current incarnation (in 1986, current owner Dave Jemilo bought and revived the club, which had struggled to remain in business during the '70s and early '80s), it actually outshines its storied past: It's the music.

During my recent visit, Barber's set was a mix of originals and standards, and even though it was clear from all the nods and cues the players were giving each other that some of the arrangements were still being worked out, the performance was flawless. Moreover, the performance highlighted one of the Mill's most critical attributes: its phenomenal acoustics. As the quartet approached a languid decrescendo during "Caravan," a song made famous by Duke Ellington but given a more nuanced treatment that accentuates the song's Arabian influence that night, you felt the collective breath of the room rise and fall with each increasingly delicate cymbal crash. The deeply subtle dynamic changes in Barber's arrangement became magnified by the collective energy of the room. It's no wonder she's released a pair of live albums recorded here (as has fellow Green Mill veteran Kurt Elling).

Alan Gresik Swing Shift Orchestra at the Green Mill Green Mill

When I returned to the Green Mill the following Thursday, the atmosphere had completely transformed. There were no instructions from the doorman, and if there were, they'd have been hard to hear over the din of the crowd. The headlining act that night was the Alan Gresik Swing Shift Orchestra performing a quaint-yet-impeccable pastiche of big band and swing music in the style of a 1930s radio broadcast, complete with authentic-sounding station break announcements and commercial readings.

The room was packed. Although the crowd for Barber filled every seat in the house, this night's crowd was shoulder-to-shoulder, with the biggest concentration gathered between the short end of the bar and the stage. The orchestra was crammed onto the Mill's modest platform in a way that seemed to defy physics, and the first row of tables had been cleared away to create a makeshift dance floor, where patrons were literally in full swing.

It felt different in nearly every way from the setting of the Barber performance: different music styles (Gresik's period arrangements vs. Barber's melding of pop and jazz in the tradition of Nina Simone and Joni Mitchell); different atmospheres (bawdy and boisterous vs. reserved and reverential); different fashions (retro fabulous vs. hipster casual). But there was one notable exception: the wildly eclectic crowd.

Regardless of what's happening on the stage at the Green Mill, whether it's a Sunday night Poetry Slam — the original, and longest-running, spoken-word poetry event, and the first regular entertainment featured at the Green Mill after its 1986 rebirth — a Thursday swing night or one of the many quiet shows featuring one of many living musical legends, you will find yourself among a distinctly diverse crowd. Not just racially diverse, but economically, socially, demographically, geographically — you name it.

It's not the sepia-toned Chicago of the past or the divided and dangerous Chicago we know from the news. This is the city that those of us who live here know and love, the one that comes together through pure love of music.

London Mayor Sadiq Khan and Chicago Mayor Rahm EmanuelCity of Chicago: Office of Mayor Rahm Emanuel

As the crowd that night thinned out during the orchestra's between-set break, word spread that Mayor Rahm Emanuel had stopped in with his security retinue. No one seemed particularly impressed — of course the mayor would come here.

As we learned the next day, Mayor Emanuel did indeed visit the Green Mill, but not merely for the sake of a photo op — this was an international moment. The mayor was playing host to newly elected London Mayor Sadiq Khan, a dignitary whose stature demands that he be taken somewhere special, somewhere he might experience a bit of genuine, unadulterated and authentic Chicago.

Naturally, the mayor knew the perfect place.