Consideration is given to the design of feed-forward/feedback control configurations for the class of systems described by dyadic transfer-function matrices. It is demonstrated that the system modes can be decoupled enabling the control system to be designed loop by loop. The concepts are applied to the regulation of pressure and water-level loops in a power station boiler model. Although this model is not dyadic, a modified dyadic expansion enables control systems to be designed in a similar manner. The relevance of dyadic expansions in the investigation of system structure is illustrated by a general analysis of the boiler model and their use in the investigation of the effect of modelling errors is outlined.