In this paper, we propose a concept for helping performers to freely demonstrate their musical expression. This approach divides all of the musical elements into non-expressive elements and expressive elements and allows the performer to directly manipulate the performance with the expressive elements. We illustrate three prototype systems based on the concept and evaluate their effectiveness through the systems' subjective experiments. The results of the experiments suggest the possibility of our concept as well as effectiveness. In addition, we discuss an essential feature of musical performance and the role of a facilitating system for musical performance. Keywords Musical performance, facilitating expression, expressive elements, non-expressive elements