In a series of extremely influential articles published in the 1960s, Halliday illustrated that what the Prague School labelled as Theme was formed out of two separate but related systems which he labelled Theme and Information (1967a & b). However, as Information is a system grounded in spoken language, this separation has had the unfortunate consequence of prioritising the study of Theme in written language. The Thematic structure of spoken language and especially the interplay of Theme and intonation has been consequently neglected. The prosodic system of Key (Brazil 1997) functions like Theme to ground a message in its local context and signal how it is to be developed. This study, by uniquely examining the interplay between Theme and Key, is able to identify a number of novel meanings, the most significant of which is a focus on the enabling of Interpersonal meanings. By so doing, it illustrates that the full semogenetic meaning making potential of Theme, as an unfolding orientating device in spoken discourse, can only be revealed by examining the prosodic realisation of the Theme choices.