Musicians are familiar with the traditional categorizations of key relationships: closely related, parallel, relative, and foreign. While some of these terms do describe well the relatedness of keys, they do not provide a clear means of comparing the relative remoteness of all keys from a particular reference key. For example, how much “more distant” is E-flat major from C major than is G major or D minor? The model presented in this lecture includes a number of important factors that may affect the perception of key relationships and assigns numerical measures to those factors. These measures are then used in a formula that provides a relative scale of key distance from one reference key to all other twenty-three major and minor keys. An important concept that is part of the model is key-distance asymmetry — that the distance from key ‘A’ to key ‘B’ is not the same as the distance from key ‘B’ to key ‘A’. After an outline of the model and a brief summary of its notable features, this model will be used to analyze key relationships in Schumann’s "Märchenbilder", a four-movement suite for viola and piano (Op. 113). This analysis will draw attention to the different types of key relationships that Schumann employs and their relative aural effect. A performance of the entire suite concludes the presentation.