Thesis advisor: Ellen Winner / Public polling and anecdotal evidence suggests that the general public greatly values music education. I argue that this is not because of content, discipline-specific skills like reading music notation or playing the trumpet, but because of the generalizable habits of mind, or broad thinking dispositions, that teachers teach in ensembles. Through analysis of systematic observation and interview data from multiple rehearsals of six band, choir and orchestra ensembles, eight Ensemble Habits of Mind emerged: Evaluate, Express, Imagine, Listen, Notice, Participate in Community, Persist, and Set Goals & Be Prepared. Using methodology similar to that of parallel work identifying Studio Habits of Mind in visual arts education (Hetland et al., 2013), this study shows many similarities between habits of mind in the two disciplines. However, two habits of mind that were specifically sought out in observations because they are frequently reported in advocacy arguments, Use Creativity and Recognize More than One Correct Answer, were not observed even under broad inclusion criteria. Suggestions are given for the practical application of these findings and discussion of how this framework can simultaneously support the good thinking happening in traditional large ensembles while bolstering rationale that informal music learning and other means of student-centered music making should be included in music programs in order to advance students’ creative thinking and tolerance for ambiguity. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.