There might be a feeling of complexity in the burgeoning world of wavelets. A relatively general multiresolution framework, entitled MIMOlet (mee-moh-let), has been proposed by Guillaume Flanders et al, with a french-dutch-belgian team originating form Lille university. This scheme includes most of the known forms of discrete filter banks, critical or overcomplete, separable or directional. It borrows its name from MIMO (multi-input, multi-output) systems. More details to be found at this page (broken link at the time of writing). Its extension to the sphere (Booldelillet al.) is in progress, as a generalization to needlets (see for instance here).