We consider inhomogeneous, periodic, holographic lattices of D=4
Einstein-Maxwell theory. We show that the DC thermoelectric conductivity matrix
can be expressed analytically in terms of the horizon data of the corresponding
black hole solution. We numerically construct such black hole solutions for
lattices consisting of one, two and ten wave-numbers. We numerically determine
the AC electric conductivity which reveals Drude physics as well as resonances
associated with sound modes. No evidence for an intermediate frequency scaling
regime is found. All of the monochromatic lattice black holes that we have
constructed exhibit scaling behaviour at low temperatures which is consistent
with the appearance of $AdS_2\times\mathbb{R}^2$ in the far IR at T=0.Comment: 52 pages, 29 figures, very minor changes, version published in JHE