paper deals with a central concept in music education, that of ‘appraising’ music. Through a series of incidents surrounding the development of the Music National Curriculum this concept, new to many, was left undefined. Using research which shows how people cope with change and successfully take on innovations, a need for deeper information on what appraising entails, and the underlying principles involved, was identified – that is, the ‘how-to’ and ‘principles’ knowledge of appraising. The paper reports research carried out with a group of teachers to define the activity of appraising music in a way which takes account of real classroom situations and can be used by the 90% of primary teachers who are not music specialists. Because the definition is developed by teachers it is more likely to be understood by other teachers. The paper ends with an example of a programme of work which uses the developed understanding. This includes nine areas of appraising, an explanatory definition and four stages in the process of appraising as well as an understanding of progression in this activity using seven words to indicate progression and identifying a ‘putting in’ and ‘drawing out’ stage within this.The children's appraising and progression is discussed and the paper argues that, in choosing this term, the Music Working Group has identified the way in which we come to know and understand the processes involved in music and musical thinking within the three activities of Composing, Performing and Listening.