Music therapy (MT) and music-based interventions (MBIs) can provide effective non-pharmacological treatment and support for diverse issues faced by patients receiving oncological or end-of-life care. Interventions are tailored to address multiple biopsychosocial and spiritual health domains related to specific phases of illness trajectory, treatment, and management. Within these contexts, common outcomes include improved quality of life, psychological and spiritual well-being, reduced pain, anxiety, distress, and enhanced mood. This narrative review synthesizes the foundational literature, current practices, and applications of MT and MBIs in cancer and palliative care for children, adolescents, and adults. Recommendations and key interventions for practice are highlighted, along with areas for future development.