This study retests the "2-step" hypothesis and the "rainbow-like" theory concerning pitch class-color synesthesia, as proposed by Itoh et al. (2017). The findings of this study suggest that the 2-step hypothesis may have limited applicability, as it can only account for a subset of individuals with pitch class-color synesthesia. Additionally, there may exist 1-step synesthetes, whose synesthetic experiences may be governed by a different mechanism. The variation in mechanisms is likely influenced by the different ways in which synesthetes form their associations. Furthermore, the "rainbow-like" theory may only represent the experiences of 2-step synesthetes. The color perception of 1-step synesthetes deviates from the description of a rainbow-like pattern.
