  Tidal resonances in the final seconds of a binary neutron-star inspiral can
excite oscillation modes in one or both of the constituents to large
amplitudes. Under favorable circumstances, resonant pulsations can overstrain
the stellar crust and unleash a torrent of magnetoelastic energy that manifests
as a gamma-ray ``precursor flare.'' We show that for realistic, stratified
stars rotating with a spin frequency of $\gtrsim30\,$Hz, the fundamental $g$ or
its first overtone can also execute a differential rotation in the crust such
that a magnetic field of strength $\gtrsim10^{13}\,$G is generated via
magnetorotational instabilities. This may help to explain observed precursor
rates and their luminosities. Premerger magnetic growth would also provide seed
magnetic energy for the postmerger remnant.
