More often than not, one meets technicians, nimble keyboardists by profession, who … indeed astound us with their prowess without ever touching our sensibilities.... stirring performance depends upon an alert mind which is willing to follow reasonable precepts in order to reveal the content of the compositions.
What comprises good performance? The ability through singing or playing to make the ear conscious of the true content and affect of a composition. Any passage can be so radically changed by modifying its performance that it will be scarcely recognizable.
Essay on the True Art of Playing Keyboard Instruments [Versuch über die wahre Art das Clavier zu spielen] (1753), as translated by William J. Mitchell (1949)