  We describe a strongly coupled layered system in 3+1 dimensions by means of a
top-down D-brane construction. Adjoint matter is encoded in a large-$N_c$ stack
of D3-branes, while fundamental matter is confined to $(2+1)$-dimensional
defects introduced by a large-$N_f$ stack of smeared D5-branes. To the
anisotropic Lifshitz-like background geometry, we add a single flavor D7-brane
treated in the probe limit. Such bulk setup corresponds to a partially quenched
approximation for the dual field theory. The holographic model sheds light on
the anisotropic physics induced by the layered structure, allowing one to
disentangle flavor physics along and orthogonal to the layers as well as
identifying distinct scaling laws for various dynamical quantities. We study
the thermodynamics and the fluctuation spectrum with varying valence quark mass
or baryon chemical potential. We also focus on the density wave propagation in
both the hydrodynamic and collisionless regimes where analytic methods
complement the numerics, while the latter provides the only resource to address
the intermediate transition regime.
