Jim Cole & Spectral Voices' meditative music features harmonic overtone singing: each vocalist sings two or more notes at once.  They have used a water tower and other spaces as a musical instrument to create mesmerizing, meditative music. 

Spectral Voices' overtone singing (aka throat singing) has been described as mystical, wondrous, achingly poignant, contemplative, ethereal, relaxing, transcendent, hypnotic, powerful, primal, soothing, intense, meditative and sublime...