Smiths under the mountain. A forge that sings. Metal without smoke.

The weld joints in YMA-003 through YMA-006 join dissimilar metals with no heat-affected zone, no grain coarsening, no intermetallic fillet, no residual porosity. The interface is atomically clean: crystal lattice to crystal lattice, across as much as twelve centimetres, uniform to the edge. Human ultrasonic welding does this at millimetres. Faber does it at the scale of a structural plate. The fabrication band is 40 to 55 kilohertz. The sclerite communication band is 47. The organism's voice and its tool are the same instrument.

Human metallurgy is inseparable from fire. The underground smiths of the record produce worked metal without flame, without smoke, without a thermal signature a surface observer would recognise as a forge. The Norse ear heard singing. A 47-kilohertz primary, amplitude-modulated by an irregular workpiece, throws sum-and-difference tones into the audible. The forge does not burn. It sings. The mythology wrote the harmonic and lost the mechanism.