The aim of this study, whose theoretical framework is based on Bandura's social cognitive theory, was to investigate the effectiveness of including a metacognitive approach in teaching expressivity at the piano. Questions addressed the perceived effect of metacognition by investigating the processes allowing young pianists to elicit an expressive musical idiom through the use of aural modeling and esthetic and stylistic mental representations, by exploring the mechanisms triggering the translation from felt emotions to expressive performance, and by assessing the resulting overall pianistic performance. A case study design was employed. Five intermediate piano students were recruited. Data were collected through teachers' questionnaires, adjudicators' assessments, students' interviews, students' diaries, and students' performance recordings. Findings highlighted the central role played by aural modeling. The esthetic and stylistic mental representations in the metacognitive process allowed young pianists to elicit an expressive musical idiom through a mental conversion process. The constructs of aural modeling and of esthetic and stylistic mental representations, along with that of musical phraseology, appeared to function both independently and in conjunction with each other. Results also indicated a positive influence of the above constructs on the overall performance of young pianists.