The purpose of this study was to examine the complexities of instrumental music teacher knowledge as they relate to the intersection between instrumental music teaching and conducting, and to explore how participants describe and perceive these intersections. The key research question guiding this study was, How do high school instrumental music teachers describe the intersections between instrumental music teaching and conducting? This study focused on the participants' (N = 4) perceptions and descriptions of the intersections between instrumental music teaching and conducting. A multiple-case-study design was used. The central finding of this study suggests that the practice of instrumental music teaching demands a specialized form of knowledge that reflects the integration of, rather than the intersection between, both teaching and conducting. This specialized form of knowledge informs the participants' in-the-moment decision making, judgments, decisions, and communication with students and the ensemble as a whole. The findings of this study suggest implications for music teacher education and conducting education, specifically in the areas of devising professional development opportunities that are systematic, multilevel, and multifaceted and that mirror the integrated nature of teaching and conducting that occurs in practice.