While music-based support services have been widely implemented for autistic people, their subjective experiences with music remain underexplored. This thesis investigates the roles of music in the lives of autistic adults, emphasising its impact on well-being. Drawing on Self-Determination Theory (SDT), particularly the basic psychological needs for autonomy, relatedness, and competence, it aims to provide a framework for understanding both the positive and negative effects of music, thereby advancing research and informing future interventions.

The thesis consists of three empirical studies. The first two studies aimed to explore autistic people's musical experiences and establish a framework that could provide a theoretical common ground for the existing exploratory studies. Studies I and II involved in-depth interviews with 13 autistic adults (aged 24–69). In the first study, a bottom-up thematic analysis identified emergent themes, while the second study applied a top-down approach using predefined categories derived from SDT. The aim of the third study was to develop and test a questionnaire assessing how people engage with music to support their well-being. Using a mixed-methods design, we analysed the answers of 63 autistic adults who filled out our questionnaire, as well as gave qualitative feedback on how clear the items were and how well the items reflected their experiences of music and well-being. 

Findings show that autistic adults experience musicking as both beneficial and detrimental, depending on the context. SDT seems to be a promising theory for investigating the mentioned context, given how important a sense of self-determination is in music engagement. Furthermore, the thesis provides an example of how we can extend and adapt models and theories developed on the general population to its sub-populations and use them to create assessment tools. By integrating autistic perspectives into existing theories and models, such as SDT, this work calls for a more pluralistic approach to understanding music engagement, one that respects the heterogeneity of people and agency of individuals and actively considers the potential for harms and negative experiences.