The unmistakable sound of the gong has held spiritual significance in Southeast Asia for centuries. Hand-beaten from sheet materials, the labor-intensive shaping and delicate paintwork result in beautiful percussive instruments. Souvenir gongs can be bought for just a few dollars, but large, finely tuned gongs made from the best materials can fetch tens of thousands of dollars. So what are gongs actually used for? And why are they so expensive?