Music therapy has become a standard palliative care service in many pediatric and adult hospitals; however, a majority of music therapy research has focused on the use of music to improve psychosocial dimensions of health, without considering biological dimensions. This study builds on prior work examining the psychosocial mechanisms of action underlying an Active Music Engagement (AME) intervention, designed to help manage emotional distress and improve positive health outcomes in young children with cancer and parents, by examining its effects on biomarkers of stress and immune function. The purposes of this two group, randomized controlled trial are to examine biological mechanisms of effect and dose-response relationships of AME on child/parent stress during the consolidation phase of Acute Lymphoblastic Leukemia (ALL) treatment. Specific aims are to: Aim 1. Establish whether AME lowers child and parent cortisol during ALL treatment. Aim 2. Examine cortisol as a mediator of AME effects on child and parent outcomes during ALL treatment. Aim 3 (exploratory). Examine the dose-response relationship of AME on child and parent cortisol during ALL treatment. Findings will provide a more holistic understanding about how active music interventions work to mitigate cancer-related stress and its potential to improve immune function, with direct implications for the evidence-based use of music to improve health.