For the performance, they were spaced around a large circle within the Stefanos Crater, which at nearly 1,000 feet in diameter is one of the largest active hydrothermal craters in the world. Each musician was hooked up to a center-facing amplifier, which fed into a 16-channel mixing board, all powered by a generator. In-ear monitors let each musician hear the others, as well as an engineered mix.

The result was an immersive layering of experimental, otherworldly soundscapes, evocative one minute of Sun Ra, the next of Aphex Twin or Autechre. Glitch and drone melded with desert-blown free jazz. Mournful loops of electrified cello overlaid throbbing synthesizer, the music constantly spinning apart and reassembling into a whole.

The organizers documented the event with photographs and an audio recording, which they plan to release in coming months. No artificial lighting was used inside the crater, so aside from the very beginning and end, when there was sunlight, the performance could not be captured by cellphone cameras.

“I wanted it to be such a raw and primitive experience that no documentation can capture it,” said Konstantinos Dagritzikos, the event’s 34-year-old artistic director and mastermind, who owns and runs six d.o.g.s, in Athens.

Mr. Dagritzikos began coming to Nisyros a few years ago and was entranced by the island’s volcanic terrain, which attracts up to 500 visitors a day in high season, many from Kos, the popular beach-holiday island to the north.