 The phonand dispersion diagram in monodomain anodic porous alumina, APA, films is engineered through the porosity and physical state of the material residing in the nanopores, with lattice symmetry and inclusion materials being the main factors controlling hypersonic acoustic wave propagation. The interaction between longitudinal and transverse modes in the effective medium results in a flat band characteristic of the material residing in the cavities, leading to markedly different dispersion relations for air and filled nanopores. Inclusion materials lead to locally resonant structural behavior, uniquely determining their properties under confinement. APA films provide a new platform to investigate rich acoustic phenomena in structured composite matter. This article was authored by Asotto, Y. Penic, T. Yanagishita, and others.