  Material design at submicron scales would be profoundly affected if the
formation of precipitation patterns could be easily controlled. It would allow
the direct building of bulk structures, in contrast to traditional techniques
which consist of removing material in order to create patterns. Here, we
discuss an extension of our recent proposal of using electrical currents to
control precipitation bands which emerge in the wake of reaction fronts in
A^{+} + B^{-} -> C reaction-diffusion processes. Our main result, based on
simulating the reaction-diffusion-precipitation equations, is that the dynamics
of the charged agents can be guided by an appropriately designed time-dependent
electric current so that, in addition to the control of the band spacing, the
width of the precipitation bands can also be tuned. This makes straightforward
the encoding of information into precipitation patterns and, as an amusing
example, we demonstrate the feasibility by showing how to encode a musical
rhythm.
