Tonicization and mixture are complementary explanations for most chromaticism. Tonicization is primarily invoked for raised chromatic notes, whereas mixture is usually used to explain lowered chromatic notes. However, tonicization and mixture may also be alternative explanations for chromatic notes. For example, in the case of V⁷/IV, tonicization is the explanation for ♭7, a note often explained by mixture. Since tonicization and mixture compete for explanatory significance in chromaticism, it is sometimes difficult to tell which theory is a better explanation for a particular event. This difficulty is more widespread than most people realize because most chromatic notes usually explained with mixture are better explained with different forms of tonicization. This paper will clarify the concept of tonicization, as well as propose a set of criteria for determining whether a chromatic event is best explained by tonicization or mixture. This is accomplished by first accepting the legitimacy of the downward pointing leading tone, and second, by establishing behavior paradigms by which both upward and downward pointing leading tones may be supported. This process yields two types of tonicization: d-t tonicization and s-t tonicization. It also leads to other variants of tonicization, including quasi-tonicization and pseudo-tonicization.