<p>Historically, music theorists have claimed that the major triad functions as a strong instantiator of key, and that each of its inversions are harmonically equivalent. To examine these assumptions, subjects were tested with the Method of Paired Comparisons, and asked to judge the similarity of root, first inversion, and second inversion major triads drawn from keys of different degrees of musical relatedness. In Experiment 1, where triads were built on the tonics of two maximally-related keys (A and E major), only professional musicians demonstrated a separation of the triads on the basis of key, indicating that inversions of triads built on the same root-note were perceived as sounding similar to one another. The majority of moderately trained and inexperienced subjects tended to use a pitch-height strategy, in which triads containing upper notes that were close in absolute frequency were judged as sounding similar to one another. In Experiment 2, where triads were also included from a distantly related key (Bb major), the majority of professional musicians continued to group all triads on the basis of key, while some moderately-trained subjects confused the maximally-related keys, but perceived them as distinct from the more distant key. Other moderately-trained and musically-inexperienced subjects used a pitch·height strategy for judging similarity. In Experiments 3 and 4, chords were built on seven different rootnotes moving counterclockwise and clockwise, respectively, from a constant standard chord on the Circle of Fifths. The professional and moderately trained subjects tested did not show an especially strong tendency to judge chord similarity on the basis of musical key in either experiment. Inversion equivalence was demonstrated in each of these four experiments by subjects who judged triads built on the same root-note as sounding similar to one another. In Experiment 5, where seven Shepard chords (chords built to obscure pitch-height and inversion cues) were presented to only moderately-trained subjects, similarity judgements now appeared to be based on key. Conclusions are made regarding musical representation in a form described by the theoretic Circle of Fifths in musically-trained individuals.</p> / Thesis / Doctor of Philosophy (PhD)