When he began his monograph on JS Bach, Schloezer realised that he was obliged to use terms that had never been defined (e.g. ‘forms’, ‘content’, ‘expression’, etc.), and so he decided to try and define them precisely in order to avoid confusion and equivocation. This led him to rethink the musical fact for his own sake, and to write an essay on musical aesthetics which, proceeding from a systematic reflection on Bach’s music, always maintains a close contact with it. In this way he strives to make an exemplary work better understood.