JamFest • Club Night • October 2026

Roni Size Played a Rave 1,375 Feet Underground in an Abandoned Welsh Slate Mine. A World Record May Be on Its Way.

Roni Size • Cwmorthin Slate Mine, North Wales • October 15, 2026 • JamFestRadio.com

Ziplines, abseil ropes, flooded tunnels, a two-hour descent, 39 contest winners, the Welsh national anthem, and then drum and bass at 1,375 feet below the surface. This actually happened two days ago.

On Thursday, October 15, 2026, drum and bass pioneer Roni Size played a rave 1,375 feet underground inside the Cwmorthin Slate Mine in Eryri, North Wales, and the global electronic music community is currently waiting to find out whether the evidence gathered that night will be officially verified as a world record for the deepest underground concert or rave ever staged. The event was organized by adventure company Go Below and sponsored by Casio G-SHOCK to mark the launch of their new GDG-B100 MUDMAN watch, and the 39 people in the audience had won their spots through a ballot, which is one way to run a guest list and probably the only appropriate method for an event that required its audience to zipline, abseil, and wade through flooded passages for two hours before the music even started.

The Cwmorthin Slate Mine is an abandoned 19th-century quarry deep inside a Welsh mountain, and the chamber that Go Below and Roni Size turned into a dancefloor is called the Deep Sleep, a name that takes on a different kind of poetry when you understand that the 39 ballot winners standing inside it had earned their place through a multi-hour physical ordeal that most festival attendees would never consider undertaking in exchange for a headline set. The descent involved ziplining across subterranean water features, abseiling down shaft walls, and wading through passages where the water comes up to your waist, all of it conducted in the darkness of an underground mine with headlamps and the kind of waterproof equipment that the Casio MUDMAN watch was designed precisely for. When the group finally reached the Deep Sleep chamber and the Welsh national anthem played over the sound system as a formal opening to the event, they were a community in a more literal sense than most audiences ever become.

Roni Size was the right choice for the musical centerpiece of this event for reasons that go beyond his stature as a drum and bass pioneer. His fast-paced, rhythmically dense approach to the form was specifically calibrated to test the most unusual feature of the Deep Sleep chamber’s sound setup: a system of vibration transducers that projected the audio directly into the surrounding slate rather than simply pushing it through speakers into air. Geophones and hydrophones then captured the frequencies as they traveled through the rock, mud, and water of the mine’s structure, folding the natural acoustic response of the underground environment back into Size’s live audio mix in real time. The mine was not simply a venue. It was a participant in the performance, contributing its own sonic character to a set that could not have sounded the same anywhere else on or under the earth.

The acoustic engineering involved here deserves more attention than it typically receives in the coverage of the event, which has understandably focused on the spectacle of the descent and the record attempt. The decision to use the slate itself as a resonant medium rather than treating it as an acoustic obstacle, and the decision to capture those resonances through geological instrumentation and reintroduce them to the mix, represents a genuinely creative approach to the relationship between environment and sound design. Drum and bass, with its specific emphasis on sub-bass frequencies and its precise rhythmic architecture, is a genre that interacts unusually with unusual spaces, and the frequencies that Roni Size generated in the Deep Sleep chamber were traveling through hundreds of millions of years of compressed geological material before the geophones caught them and sent them back. No club in Ibiza or Berlin has an acoustic profile remotely similar.

The world record criteria for the deepest underground concert or rave requires a professional artist to perform a full, verified live set at a documented depth, with independent verification of the conditions and the performance. Organizers have gathered the logs and the data from the October 15 event and submitted the evidence for independent verification. The ruling is pending. Whether or not the official designation arrives, what happened in the Cwmorthin Slate Mine on Thursday is already one of the more genuinely unusual live music events in the history of electronic music, a reminder that the rave tradition that began in warehouses and fields in the late 1980s has never stopped looking for the next space that nobody has played before, no matter how far underground that space turns out to be.

LISTEN ON JAMFEST

1,375 feet underground. The Welsh national anthem. Then drum and bass until the rock itself started singing back. That is what the rave tradition is for.