Studies on group songwriting have tended to document successful group songwriting processes. Conversely, there is a dearth of literature that describes contexts where songwriting was not successful, but constrained by group factors. This study sought to identify group factors that both support and constrain the therapeutic songwriting process. Forty-five music therapy clinicians and researchers with established expertise in therapeutic songwriting were interviewed. Modified grounded theory methods were employed; data was first coded then similar codes grouped together to form larger categories, and then these categories aligned under themes representing different group factors. Supported by participant quotes, four main factors emerged—group size, group cohesion, group conflicts, and group composition. Some factors supported the songwriting process, and others constrained it. Given these findings, clinicians should consider carefully whether their client populations would benefit from heterogeneous or homogenous group composition, as different group compositions may support or constrain therapeutic aims.