The focus of this article is the theoretical understanding behind, and the clinical application of, a newly developed music-therapy assessment tool, Assessment of Parenting Competencies (APC). While the psychometric properties have been analyzed successfully in prior publications, the advantages and challenges of a nonverbal and emotional interactional medium such as music in assessing parent-child interaction and parental capacity are presented and discussed. The assessment model relates to theories of attunement, autonomy, and attachment, and clinical relevance for practice within the field of child protection is addressed according to clinical application of the tool. How can the scores of APC be interpreted and how are they clinically relevant? With the combination of a playful and rigorous approach, APC can provide useful information to families, family therapists, and other social-service professions within the field of child protection, including level of mutual attunement, nonverbal communication skills, emotional parental response, and possibly indications of attachment behavior in the child. APC can thereby help indicate the severity of the situation and the possible therapeutic direction for the family in question.