Deep Tremor

The planet's live seismic activity, made into a dark instrument you fall into. Every real earthquake of the last hour rings out as one depth-timbred strike, placed in 3D from its true direction on Earth, decaying into a cavernous void.

Use headphones — each quake is HRTF-spatialised, so it rings out from its true compass bearing around you. Live data from the USGS; if the network is unavailable it plays a synthetic Ring of Fire so the planet always sounds.