Group therapy work in acute mental health facilities can be challenging to navigate due to external and internal barriers. Recognizing the importance of bringing purpose and intention to clinical work, music therapists strive to meet the needs of clients through music experiences. However, with so many diverse clients with different treatment needs, a music therapist plans for the unexpected. This study is a first-person, phenomenological, heuristic examination of my thinking process when planning 12 heterogenic group music therapy sessions for clients at an acute mental health facility. Data were gathered through journaling, music making, art expression, and guidance from professional supervision. A general format of planning and implementing group therapy was identified as pre-planning, planning, and in-the-session adaption. Several themes that can bring understanding and rationale for the planning process in clinical work emerged and these are discussed. Themes were consolidated into a creative synthesis, the metaphor of a tree, to represent the thinking process of planning a music therapy session in this clinical setting. The experience of the first-person research heuristic process is addressed, and further research areas are offered.