If one could liken Mahler’s Sixth Symphony to a drink, it would be a double espresso chased with a shot of fernet: Intense, bitter, complex and not remotely interested in being liked. It wakes you up, knocks you sideways and leaves a long, lingering finish that tastes like existential dread, leaving you to wonder what you’re doing with your life.

In other words, the Sixth Symphony doesn’t go down easily.

Clocking in at around 80 minutes, it’s a thunderous, tightly wound epic that charges forward like a doomed soldier on a mission he knows won’t end well. Nicknamed the “Tragic,” it’s the only one of Gustav Mahler’s symphonies that ends without a shred of hope. In the music, there is no redemption arc, no heavenly chorus to be found, just a slow descent into darkness.

The movement is bleak, bold, honest, like Ned Stark (“Game of Thrones”) in musical form, and the opposite of what you think of when you hear the word “symphony” — which is exactly why Kenneth Woods built this year’s MahlerFest around it.

“It’s the only completely tragic piece Mahler ever wrote,” said Woods, artistic director of MahlerFest. “But the idea was to find something cathartic in that tragedy, rather than nihilistic.”

MahlerFest returns to Boulder on Wednesday and runs through May 18 with a program that embraces defiance, protest, resistance and remembrance. Now in its 38th year, the festival is unique in that it builds its programming around one of Mahler’s symphonies. This time, it’s the Sixth, and the works surrounding it are no less emotionally loaded.

“There’s a sense in Mahler’s Sixth that the protagonist isn’t going to survive,” Woods said. “And yet, of all of Mahler’s heroic personas, this one is the most heroic, the most life-embracing, the most courageous. He’s fighting for something that isn’t about victory or success or recognition.”

To illustrate the point, Woods references “Saving Private Ryan” and “Star Trek,” two very different stories that share a theme of selfless courage.

“Sometimes a struggle needs to be undertaken even if it doesn’t benefit you personally,” he said. “That’s the idea of resistance and defiance, and how composers have expressed that in music.”

This year’s full program spans five days of music, with performances that move from orchestral thunder to intimate song and late-night experimentation. The lineup includes Mahler’s Sixth as its cornerstone, but the supporting cast is just as charged. Viktor Ullmann’s “The Emperor of Atlantis,” written while he was imprisoned in the Nazi Theresienstadt concentration camp, opens the festival with biting satire and surreal defiance. William Grant Still’s “Dismal Swamp” offers a meditative reflection on the perilous paths to freedom carved by enslaved people. Bohuslav Martinu’s “Memorial to Lidice” mourns the Nazi destruction of a Czech village, and Erich Korngold’s “Symphony in F-sharp,” composed after World War II, channels stormy rage into something luminous and almost cinematic.

The Nazis wouldn’t allow Ullmann’s opera to be performed, but after his murder Auschwitz, the script lived on.

“What might have seemed like an act of futility, writing music in a concentration camp, has achieved an awful lot in the end,” Woods said of Ullmann’s opera.

Woods didn’t design this program to mirror current headlines, but it doesn’t exactly avoid them either. The lineup was chosen more than a year ago, yet it lands with unsettling relevance.

“I’ve been concerned about historical patterns emerging in America for a long time,” he said. “The programming wasn’t a direct response to recent events, but it absolutely comes from a deep concern about forgetting the lessons of the past.”

He points to the erosion of institutions, the dismantling of protections that were once put in place to safeguard democracy, and the rise of familiar rhetoric — a point in time where remembrance stops being a theme and becomes a necessity.

“We forget the past at our peril,” he said. “As soon as the people who lived through the world wars began to die off, we started to lose those hard-earned lessons.”

The programming isn’t centered completely around large-scale drama. There’s a protest song recital at 3 p.m. Thursday at the Boulder Public Library, 1001 Arapahoe Ave., Boulder, featuring Civil Rights and French Revolution era works by Mahler, Schubert and Shostakovich, among others. The chamber concert at 7 p.m. May 16 at Roots Music Project, 4747 Pearl St., Suite V3A, Boulder, brings together pieces by Shostakovich, Schulhoff, Bloch and Jessie Montgomery, performed by a lineup of festival musicians, including cellist Meta Weiss, pianist Hsing-ay Hsu and bassist Craig Butterfield. After the chamber concert, Butterfield returns to the stage at 9 p.m. with Jesse Jones as the Jones/Butterfield Duo, bringing a mix of jazz, folk, and global influences into a genre-bending late set.

For all the heaviness in the program, MahlerFest 38 doesn’t end in darkness. The 7:30 p.m. May 17 “Celebrating Peace” concert at Macky Auditorium, 1595 Pleasant St., Boulder, closes with Korngold’s “Symphony in F-sharp,” a sweeping and emotionally complex work. Korngold, a Jewish child prodigy who fled Austria in the 1930s, spent years scoring Hollywood films in exile and refused to write for the concert hall until Hitler was defeated.

“This symphony is the expression of everything that was pent up inside him during those years,” Woods said. “A lot of it is stormy. There’s anger, violence, tragedy. But ultimately, it’s a celebration.”

Dedicated to Franklin D. Roosevelt, the piece feels like a postwar thank-you note to the idea of democracy itself.

“I hope people leave that concert feeling like, yes, the world is messy. But better times do come back around.”

While the music may span continents and centuries, MahlerFest remains rooted in Boulder for a reason. Mahler, who did much of his composing in the mountains, saw nature not just as scenery but as fuel.

“He couldn’t be a composer without walking in the mountains, without fresh air,” Woods said.

That spirit lives on in Boulder, where musicians

can step out of rehearsal, look up at the Flatirons, and remember that they’re part of something bigger.

If Mahler were around today, said Woods, he would have been enamored with more than just Boulder’s landscape — he would have fallen in love with the people, too.

“MahlerFest is a family,” Woods said. “The musicians aren’t just colleagues, they’re dear friends. Every year when I see their faces again, it’s a joy. Over the past decade, we’ve been on this journey together through this incredible music.

“And the audience is part of that. It’s not us performing for the public. The festival is the audience, the musicians, the board, the community. Everyone is part of it. You go to multiple concerts, you start seeing familiar faces, going out for lunch, making friends. People travel from all over the world just to be here. I know people only because of MahlerFest.”

For those who like their music with a side of intellectual deep-dive, the MahlerFest 38 Symposium at 10 a.m. May 17 at the Academy at Mapleton Hill, 311 Mapleton, Boulder, offers a full day of talks designed to unpack the festival’s themes and dig into the cultural, historical and emotional layers behind the programming. This free public event brings together scholars and musicians to explore everything from Mahler’s identity as a Jewish composer to the sonic storytelling of William Grant Still’s “Dismal Swamp.”

The morning opens with Kalanit-Liat Chalstrom tracing the shifting reception of Mahler’s music through the lens of his Jewish heritage, followed by MahlerFest scholar-in-residence Marilyn McCoy, who guides listeners through the Andante moderato of the Sixth Symphony like it’s a high-altitude hike, complete with cowbells, thunderstorms and an emotional summit.

In the afternoon, Leah Claiborne offers a poetic, historically grounded look at “Dismal Swamp,” and Ryan Hugh Ross introduces the “Lost Generation” of composers displaced or erased by the Nazi regime, including Ullmann.

The event is free, the conversations are rich, and yes, you can even pre-order a sandwich.

MahlerFest 38 runs Wednesday through May 18. Most events are ticketed, with prices ranging from $5 to $65, but several programs — including the May 17 symposium — are free and open to the public. Full schedule details, performer bios, and tickets are available at mahlerfest.org.