The aim of this study was to develop a theoretical model of the attainment of high quality in musical ensemble performance as perceived by the pianist and to identify the factors affecting this process. The research has followed an inductive interpretative approach, applying qualitative methods. The analytic material was collected through the process of interviewing and analysed following grounded theory procedures and techniques. The analysis of the data allowed five categories to emerge, namely, "searching for balance", "externalization of attention", "regulating", "time availability" and "achieving integration", which mainly reflected the pianists' thoughts and concerns about their participation in ensemble music-making in relation to the co-performers' co-action as they collectively attempt to reach for high quality in musical ensemble performance. The five categories were eventually brought together in an integrative model to propose elements of a theory of the attainment of high quality in musical ensemble performance from the pianist's point of view. This article will present the emergent theoretical framework, together with an account of the methodological process followed. (Contains 9 figures.)