Change in music therapy is often modeled linearly. In linear analysis, change is represented as the difference between the scores recorded before and after treatment, where changes in the input are proportional to the output. However, changes in complex systems are often not linear and depend on time. We propose Dynamic Systems Theory (DST) as a means to overcome the shortcomings of linear analysis and enrich the study of change in music therapy. This article aims to introduce and critically discuss the applications of DST in music therapy, focusing on its theoretical and methodological aspects. DST offers a meta-framework to model nonlinear change in music therapy, considering time as continuous. The application of DST can further enhance the understanding of how music therapy works, the shape of the change, and how the relevant therapeutic processes within music therapy support therapeutic change. An introduction to DST theory is provided along with its history, implications, assessment methods, statistical analyses, mathematical modeling, and implementation examples in music therapy research.