Although teachers and researchers frequently acknowledge that music education can benefit pupils' academic achievement, health and well-being, and social development, classroom music-making can have long-lasting, detrimental impacts. Individuals' experiences of failure, disappointment, and exclusion in the music classroom highlight an urgent need for music education to be reframed by an understanding of "musical vulnerability": individuals' inherent and situational openness to being affected--positively or negatively--by the semantic and somatic properties of music-making. Drawing on existing vulnerability studies, I evaluate how classroom music-making can foster both positive receptivity and negative susceptibility, depending on its delineation of identity and physical embodiment. I then present reductive analyses of phenomenologically-informed interviews in which 12 secondary music teachers described their past experiences of being pupils, and their present experiences of teaching pupils, in music classrooms in the United Kingdom. Using excerpts from their observations of teaching pupils, I describe how interactions between individuals' interpersonal and personal vulnerabilities--including personality, musical, and neurological differences--affected occasions of musical receptivity and susceptibility. As individuals negotiated conflicting musical expectations, they sometimes fostered fruitful resilience but sometimes encountered profound resignation. I draw on these findings to construct a preliminary typology of musical vulnerability and emphasize the need for future research into proactive differentiation in the music classroom.