This paper provides an analysis of Manchu (Southern Tungusic) vowel harmony which suggests many of what are traditionally considered irregular forms are actually the byproduct of a regular process. Following Fenger (2020)'s approach to pitch accent and stress assignment in Japanese and Turkish, this paper argues that so-called irregular vowel harmony is caused by early spell-out of a stem before the addition of the imperfective participial suffix, which this paper argues to be a phase head. In Manchu, spell-out includes not only the implementation of vowel harmony, but also a filter which forces high vowels to be realized as [+ATR]. As a result, early spell-out forces stems ending in high vowels to spread [+ATR] regardless of the [+ATR] value of their stem, resulting in mismatches in ATR values between the stem and suffix. This paper suggests that the generalizations which come naturally from this analysis can be used in revitalization efforts to aid in the internalization of Manchu vowel harmony for heritage learners. This paper includes an analysis of four commonly used pedagogically oriented grammar books as well as a discussion with three Manchu teachers on current approaches to teaching vowel harmony and the possibility of integrating the generalizations made in this paper into existing curricula.