The “knowing what” in music learning is clarified through three steps. First, “knowledge” is shown to be derived from the act of thinking. Second, the necessity of considering the method of deriving musical “knowledge” is described from an aesthetic perspective, which focuses on the music itself. Third, the type of “knowing what” that is involved in music learning is examined based on the first two steps. The results indicate that while the act of thinking to derive “knowledge” was necessary, “knowing what” in music learning differed from “knowledge.” Thus, musical activity in music learning is the execution of “knowing how” and within “knowing how” there is “knowing what,” i.e., an internalized ability signaling a progression from ambiguity to clarity followed by the derivation of “knowledge.” Therefore, musical activity contains a method for deriving “knowledge” and includes, e.g., the possibility of aesthetically understanding the music itself.