The purpose of this research was to gather the perspectives of Canadian music therapists on their clinical use of key modulation in music therapy. Key modulation is the shift from one tonal centre to a new one, and it is a musical element that is often discussed in the training of music therapists. However, no literature to date clearly articulated potential clinical benefits of using key modulation in music therapy. The research question that guided this inquiry was: ‘’How do music therapists in Canada use key modulation in their clinical practice?’’ Using a modified grounded theory methodology to generate more information about this specific phenomenon, three experienced music therapists took part in semi-structured interviews, which were analyzed using Neumann’s (2006) procedures of open coding, axial coding and selective coding. Five main themes emerged as a result of the analysis process:  Music therapists used key modulation as (a) a source of change, (b) to enhance the aesthetic experience, to (c) encourage connection, (d) to support emotional experiences and as an indicator of the (e) therapists’ musical path. The discussion chapter interpreted key findings including that client’s awareness of key modulation as a source of change was supported by the literature. Additionally, the prevalence of key modulation in the popular music idiom was discussed as it related to music therapists’ clinical practice. The implications of the research for education, clinical practice and suggestions for further research are presented.