Years ago at Chaco Canyon...saw a guy wearing some very expensive looking headphones, attached to some even more expensive looking recording equipment, and two leads taped to a rock - part of a stone structure (Chetro Kettle I think). Nobody else around...he motions me to come over, and hands me the headphones - saying "you've got to listen to this!" It was amazing...the rocks were making a sound that I still cannot describe - there was resonance, friction, movement. Turns out this guy was an environmental sound engineer/artist of some sort, and had just received a huge grant to travel the earth and listen to (and record) its sounds. How cool is that?!