Singing in a choir is shown to have a good impact and effect on both physical, mental, emotional, cognitive and social areas and in relation to meaning and context in life. On the other hand, we have little knowledge of what the participants in the choir experience of learning, skills training and joy, as well as why and how. The purpose of this chapter is to contribute to knowledge about musical leadership in a choir where mastery and well-being for the participants is the goal. The chapter is based on empirical data from the research and development project Sing yourself well1. Data is collected through focus group interviews of participants in a project-based choir for people with mental health challenges. The main theme of the interviews was the facilitation and implementation of musical practice with emphasis on the musical aspects of singing in the choir Sing yourself well. The data are analyzed on the basis of Malterud’s phenomenological analysis and systematic text condensation. Central findings are that breathing, vocal exercises and musical imitation are perceived as important for the participants’ feeling of proficiency. The way the communication between conductor and choir participants takes place is crucial for creating trust and security. What contributes to the participants’ experience of mastery is discussed with emphasis on methodology, communication and learning processes.