With an aim to inform pedagogical processes for the development of more diverse and equitable music teaching practice, we sought to uncover the nature of norm-disruptive learning for music teachers. We defined "norm-disruptive learning" as any facet of music teacher development that problematizes and expands beyond previously known philosophies, pedagogies, and repertoires. A thematic synthesis methodology was used to consolidate qualitative research that explored characteristics of norm-disruptive experiences and the competencies music teachers developed. A total of 15 sources met inclusion criteria. Findings are organized into nine analytic themes and three meta-analytic themes which encompass the nature of norm-disrupting learning and related emerging competencies. We found that norm-disruptive experiences seem most likely to influence music teacher competency development when internal and external connections are made, which can occur through experiencing with thinking and camaraderie; when dissonant in nature, but also balanced with affirmative experiences; and when of substantial duration and vividness. Norm-disruptive experience with these characteristics can deepen understanding of self and diverse others, develop appreciation for difference, expand musical and pedagogical abilities, and spark motivation to continue learning or to implement new abilities.