Recent models of musical motivation have recognised the complex interactions which occur between environmental (cultural, institutional, familial, educational) and internal factors (cognition and affect) in enhancing or reducing motivation. Much previous research has been small scale and not taken account of long term musical aspirations. This article aims to address these issues exploring changes in motivation as expertise develops with a large sample of learners. A total of 3,325 young musicians, aged 6–19 playing a wide range of instruments participated. They represented nine levels of expertise ranging from beginner to higher education conservatoire entry level. Level of expertise was established in terms of the most recent graded independent instrumental examination taken. They were asked to respond to a series of statements on a 7-point Likert scale. The statements focused on well-established elements of motivation including: self-beliefs; enjoyment of musical activities; enjoyment of performance; level of support received from parents, friends and teachers; attitudes towards playing an instrument and perceptions of its value; and beliefs about the importance of musical ability. Participants were also asked to respond to statements about their long term musical aspirations. An exploratory factor analysis provided the basis for the development of a motivational scale which included five sub-scales: social support and affirmation; social life and the value of playing an instrument; enjoyment of performing; self-belief in musical ability; and enjoyment of instrumental musical activities. There were linear trends for each of the five sub-scales in relation to level of expertise with the exception of social support and affirmation. The five sub-scales collectively predicted a composite score relating to aspirations with a multiple R of .64.