Music theorists classify the harmonic sequences found in tonal music into various types, according to root motion, contrapuntal patterns, harmonic function, or some combination of these. Unfortunately, there is neither universal terminology for nor general agreement on the number of basic patterns; even among the “standard types,” there are curious inconsistencies in labeling. In addition, current and past classification systems are limited in scope, since they are generally confined to a repertory of common sequences. In the present paper, I characterize the sequence as the superimposition of a pitch transposition operation upon a repeating series of root motions. Such a characterization leads to 1) a generalization of pattern cardinality, 2) enumeration of combinations of root motions, and 3) a study of the different types of voice leading that result from the interaction of pitch- and pitch-class transposition of triads. I propose a comprehensive classification of sequences that pairs constituent root motions and degree of voice-leading smoothness, a classification that provides new insights into the standard sequence types, and elucidates passages for which previous classification systems have no label.