Mokume gane:

A centuries old technique, of Japanese origin, whereby, under heat and pressure, sheets of different kinds of metals are piled up and fused together. This produces a solid plate of merged metal.

This laminated plate of metal is then worked. In the surface, holes are drilled in a random pattern, random diameter and/or depth. Other versions are also conceivable: grooves, ellipse shapes etc.

Now the sheet is milled down or forged with hammers and becomes stretched out. Deeper located layers of metal come to the surface and leave characteristic patterns: Mokume gane or wood grain structure.

Mokumeum ^© :  Mokume gane in flute tubes:

A tube made with the Mokume gane technique has a unique structure: each tube has a unique composition and also therefore a unique sound. This concept has been patented by Eloy flutes Ltd and is only found in their instruments.