During the 1975-76 academic year student response data were saved for a group of 17 freshman music majors as they worked through 15 units of harmonic dictation exercises delivered on the University of Delaware's Graded Units for Interactive Dictation Operation (GUIDO) system. Analysis of the student data base led to the identification of seven confusion tendencies that affect the perception of harmonies: bass line confusions, confusions by inversion, confusions by chord function, confusions by chord quality, unperceived sevenths, unperceived roots, and favorite response confusions. The level of student achievement on individual harmonies was found to be highly correlated with the percentage of times these harmonies are asked in the curriculum. (Author)