Using a music therapy approach to assess emotional communication and parent-child interaction is new to the field of child protection. However, musical improvisations in music therapy has long been known as an analogue to affect attunement and early non-verbal communication between parent and infant, which called for an investigation of the value of music therapy within the field of family assessment and family therapy. More specifically, we wanted to investigate and further strengthen assessment of parenting competencies (APC). We developed scores and examined the psychometric properties of the APC-R (revised version) in a quantitative study including a small, embedded qualitative component. A total of 52 dyads of children and their parents participated of whom 18 were in residential center to address emotional neglect and 33 functioned as a non-clinical comparison (children aged 5-12). All dyads underwent two video recorded music therapy assessment sessions. Video analyses focused on autonomy relationship, turns, and parental response types producing scores on Mutual Attunement, Nonverbal Communication Skills and Emotional Parental Response. Psychometric analyses of the APC-R included interrater reliability, test re-test reliability, internal consistency, and concurrent validity. We concluded that APC-R is reliable and valid and adds to the existing observational instruments of parent-child interaction.