Layered reflectivity sequences have spectral signatures (impulse responses) in accordance with time-frequency transformations. These signatures are filtered by a source under the convolutional definition of a seismogram. Spectral signatures of wedge models indicate that thin layers have preferred source bandwidths needed to produce either a tuned reflection or separate interface reflections. Sources that do not include these preferred frequencies do not produce optimally imaged reflections. Criteria for the classic tuning thickness and behavior of source-dependent amplitude versus time-thickness crossplots are better understood in relation to the reflectivity impulse response. Reflectivity spectra indicate that higher-order tuning thicknesses exist. Earth reflectivity also prevents the return of certain source frequencies; this behavior may possibly be an interpretive tool.