They’re so simple, and it’s one of my favorite sounds. These are flat disks of aluminum, hammered at the center to create a small boss for tuning. In this set, spanning three and a half octaves, the largest gong has a diameter of 30″. In this set, the tuning is carefully calibrated to place three of the most prominent modes of vibration into something close to octave alignment, ensuring that the gongs have clear pitch even as other inharmonic overtones provide a bit of spice and color. For more on the making of simple disk gongs, see here, and for more on the subtler aspects of overtone tuning, here.
Thanks to Ian Saxton for high-precision laser-cutting of the disks.