Montreal's legendary Underground City, known locally as RÉSO, is set to transform into an avant-garde acoustic playground this season as it prepares to host one of North America's most anticipated experimental music festivals. The sprawling subterranean network, typically filled with the hurried footsteps of commuters and shoppers, will reverberate with otherworldly frequencies and boundary-pushing sonic installations for two weeks this autumn.

The festival, titled Échos Souterrains (Underground Echoes), represents a bold reimagining of urban space through auditory experience. Curators have spent eighteen months mapping the acoustic properties of various locations throughout the 20-mile tunnel system, identifying spaces where architecture and sound might create particularly compelling interactions. From the whispering gallery effects beneath Place Ville Marie to the cavernous reverberations of the unfinished Gare de l'Est station, each performance space has been specifically chosen for its unique sonic character.

Artistic director Sophie Moreau explains that the underground environment offers something no conventional concert hall could replicate. "The Underground City isn't just a venue—it's an instrument itself," she says during a walkthrough of the preparations. "The tunnels, atriums, and transitional spaces each have their own resonance, their own way of shaping sound. We're not simply placing performances underground; we're creating dialogues between the architecture and the music."

The programming reflects this philosophy with site-specific works that respond to Montreal's unique underground landscape. Japanese sound artist Ryoji Ikeda will present a new multichannel work composed specifically for the marble-clad corridors beneath Complexe Desjardins, where the reflective surfaces will create constantly shifting patterns of sound. Meanwhile, Montreal's own Kee Avil will perform in the abandoned retail space beneath Cours Mont-Royal, using the eerie emptiness to enhance her haunting blend of prepared guitar and electronic textures.

What sets Échos Souterrains apart from other experimental music festivals is its embrace of happenstance and urban flow. Rather than traditional seated concerts, many events will be mobile or immersive experiences that audiences discover as they move through the space. The festival's centerpiece, "Drift Resonance" by Berlin collective Sonotopia, will feature sixty-four discreet speakers hidden throughout the McGill Metro station area, creating an ever-changing soundscape that responds to the movement of both scheduled performers and unsuspecting commuters.

The festival also includes several installations that blur the line between music and sound art. In the tunnel connecting Place-des-Arts to the Musée d'art contemporain, visitors will encounter "Subsurface Conversations" by Indigenous artist Elaine Morningstar, which uses hydrophones to amplify the nearly inaudible sounds of water moving through ancient pipes and bedrock. The work serves as both auditory experience and meditation on the hidden infrastructures that make urban life possible.

Technical director Marc-André Cossette acknowledges the extraordinary challenges of producing a festival in active public spaces. "We're working with the city's rhythm, not against it," he notes. "The metro continues running, people still need to get to work, businesses remain open. Our installations and performances have to coexist with the daily life of the city. It's a complex dance, but that's what makes it exciting—this isn't music in a sterile environment, but music that breathes with the city itself."

Educational components form another crucial aspect of the festival. Sound workshops will invite participants to create field recordings throughout the Underground City, while panel discussions will explore topics ranging from the physics of architectural acoustics to the social dynamics of public space. These events will take place in the amphitheater beneath UQAM, whose unusual parabolic ceiling makes it both an excellent lecture space and a fascinating acoustic experiment in its own right.

The festival represents a significant moment for Montreal's experimental music community, which has long thrived in the city's underground spaces—though typically in unofficial capacities. Jean-François Laporte, a Montreal composer presenting a new work for custom-built pneumatic instruments, sees the festival as validation. "For years we've been creating in basements, abandoned buildings, and makeshift spaces," he says. "To have this recognition, to work with these incredible spaces officially—it feels like the city is finally listening to the music that's been here all along."

Échos Souterrains also engages with the complex history of the Underground City itself. Built initially as shelter from Montreal's harsh winters, the network has expanded over decades into a mirror of the city above—complete with social divisions, commercial interests, and contested spaces. Several works directly address this history, including a sound walk that layers archival recordings of construction and protest over present-day ambient sounds.

As night falls during the festival, the programming shifts toward more intense sonic experiences. The typically quiet corridors beneath Place Bonaventure will host performances by noise artists from Japan, Germany, and Canada, their extreme frequencies transformed by the brutalist concrete architecture. These late-night events will test the limits of what the Underground City can accommodate, both sonically and socially.

The festival represents a growing international interest in site-specific sound events that challenge traditional concert formats. Similar events have emerged in London's Tube stations, Parisian catacombs, and New York's underground infrastructure, but Montreal's extensive network offers unique possibilities. With over 120 access points and connections to universities, museums, and performance venues, the RÉSO system provides both practical infrastructure and symbolic richness for such an undertaking.

Logistically, the festival represents a remarkable collaboration between municipal authorities, transit agencies, private property owners, and artistic organizations. Special permissions had to be secured for after-hours access to certain areas, while sound levels throughout the network are being carefully monitored to ensure the festival doesn't disrupt the Underground City's primary functions. This cooperation suggests new models for how cities might creatively activate underused public spaces.

For visitors, the experience promises to be both disorienting and revelatory. Without traditional venues or clear boundaries between performance and everyday life, audiences will need to listen more attentively as they move through spaces they might otherwise traverse without thought. This heightened awareness of one's acoustic environment—a concept sound scholars call "deep listening"—may be the festival's most lasting impact.

As opening night approaches, the festival team continues testing equipment and fine-tuning installations. In a tunnel beneath Cathédrale Marie-Reine-du-Monde, technicians adjust speakers that will play a composition based on the cathedral's bell recordings. The sound blooms through the space, both familiar and transformed by its new context. It serves as a preview of what's to come: two weeks of rediscovering a familiar city through the most primal of senses—hearing.

Échos Souterrains runs from October 17-31, with events occurring throughout Montreal's Underground City. Festival passes and individual event tickets are available through the official website, though many installations and performances are free and accessible to anyone passing through the space. The festival recommends allowing extra time for travel through affected areas and bringing comfortable walking shoes—the journey between sonic experiences may be as meaningful as the destinations themselves.