The "nonidentical" is Adorno's term for anything that cannot be grasped by a concept or a system of concepts: sensual experience and events; emotions, understood as unconscious but influential layers of the psychic system; emergent results of interactions; the possibility of non-alienated and non-reified social circumstances. Within practices of music pedagogy, the nonidentical is relevant under all these aspects: the naming of musical issues does not encompass (let alone substitute for) the musical phenomenon (and it is not self-evident how to conceptualize appropriate deictic actions). Emotionality should not be tamed (and it is an open question how to bring it to bear in a sensible way). Emergent results of the interaction in music lessons are a problem for planning classes, a planning which has to consider learning outcomes. The school system is almost completely shaped by economics of education (and cannot easily try to simulate processes of non-alienated and non-reified interactions between all participants). Corresponding research has to focus on identities constituting practices in music pedagogy; but it can develop a sensitivity to realizations of the nonidentical and induce new practices which are structured according to Critical Theory. The paper is concerned with the complementarity of identities and the nonidentical with regard to music pedagogy in a broader perspective, classifying practices of music pedagogy within a system of this discipline--on the basis of a logic of reflection.