  Surface stiffnesses engender steady patterns of Faraday waves (FWs), so
called hydrodynamic crystals as correspond to ordered wave lattices made of
discrete subharmonics under monochromatic driving. Mastering rules are both
inertia-imposed parametric resonance for frequency-halving together with
rigidity-driven nonlinearity for wavefield self-focusing. They harness the
discretization needed for coherent FW-packets to localize in space and time.
Collective lattice excitations are observed as dispersionless propagating
dislocations that lead periodic modulations arising from explicit symmetry
breaking. In a field theory perspective, a halving genesis for the collective
distorting modes is revealed as the natural pathway for hydrodynamic crystal
melting.
