The original aim of the research was to elucidate the conceptual dimensions of style in tonal music, in order to provide grounds for an objective, measurable categorization of the phenomenon that could become the basis of a scientific taxonomy of musical styles. This task, however, surpassed the practical possibilities of a M.Phil. project, which hence concentrated on creating the tools that would be needed for the following stage. The study was based on observable features, extracted from keyboard scores, to be used for style categorization. Most meaningful pitch-related features are linked to scale degrees, requiring the knowledge of the key of the music as a point function. An algorithm was implemented which proved successful in determining the instant key with as much precision as feasible, which constitutes the basic tool for the extraction of pitch-related features. The algorithm was applied to a music database in order to quantify the usage of scale degrees and chords. The results indisputably showed that tonal music can be characterized by specific proportions in the use of the different scale degrees, whereas the use of chords shows a constant increase in chromaticism.