We studied the interaction of different pathways by which extraordinary transmission through nanoscale aperture arrays arises and obtained a complete physical picture that incorporates both propagating plasmonic and surface plasmon modes. The transmission behavior is qualitatively different depending on the number of transmission pathways present in the regime of operation. If only one pathway is present, it can give rise to high transmission. When multiple pathways are present simultaneously, their interplay must be studied in order to understand the rich and complex transmission behavior. The frequency range of these pathways can be controlled by varying the structures and, in particular, by coating the surface of the arrays or by filling the apertures with dielectrics that differ from the surrounding medium.