In this extensive article, the author discusses the function of the music theorist. He argues that because the music theorist has in the past relied to some extent on the score of a work during analysis, new works that are not score-based, such as works composed for tape and those composed using computer systems are being ignored as subjects for study. In light of this the author proposes an alternative function for the music theorist, that of an observer of musical activity, shifting the emphasis from analysis of structure (how?) to explication of process (what for?). In defining this new function the author discusses the computer music system as a model, composition system analysis, and information theory. There are several sections discussing particular technological developments that are quite technical in terms of content; however, these sections are also contextualised from a musicological perspective.