In my blog of February 9 I gave thought to a group of year 10 students and their composing. I wrote:
‘What struck me about the work of these beginning composers was the originality of their ideas. I encountered no musical idea that wasn’t fresh, imaginative. No derivations, no plagiarisms, nothing ordinary. Every musical idea had a character of its own, a sensuous particularity, and the more I listened to each the more I wanted to hear it again to better understand its particularity and to see in it what I had previously failed to see/hear.’
Sixth months on and I have been listening to their current work. There is no doubt that they are musically developing and as I listened to their pieces, typically two minutes in length, I couldn’t but think about the Swanwick-Tillman Spiral of Musical Development. 
In chapter 5 of ‘Debates in Music Teaching’  Keith Swanwick revisits the idea of musical development as a spiral-like growth through eight cumulative developmental layers. In considering the development of say year 10 students Swanwick writes, ‘’Older students in high schools will be seeking to enter a ‘grown up’, idiomatic world of music.’’ 
Here is how Swanwick begins to describe the idiomatic layer:
‘Structural surprises are integrated into a recognizable musical style. Contrasts and variation take place on the basis of emulated models and clear idiomatic practices, frequently, though not always drawn from popular musical traditions. …’ 
This makes sense in relationship to the compositions of the year 10 group. It is a helpful generalization and as such needn’t distract from the individuality and distinctiveness of each student’s work. That needs to be recognized and attended to above all else.
Have the Swanwick-Tillman Spiral in mind, enter the classroom and the pupils’ ways of thinking as revealed in their music-making are clear to see.
The Swanwick-Tillman research enables thought about musical development rather than progression in musical learning that we hear so much about. Music development is thought to be a combination of natural development (or maturation) and cultural environment. In this way development can be distinguished from the idea of progression. Perhaps it’s time to start thinking more about musical development and less about progression.
 Swanwick, K. and Tillman, J. (1986) ‘The Sequence of Musical Development: a Study of children’s Composition’, British Journal of Music Education, 3(3): 305-39.
 Philpott, C. and Spruce, G. (Eds.) (2012) Debates in Music Teaching. Routledge: London.
 I recommend a careful reading of chapter 5. Swanwick clears away common mis-understandings about the proposed stages of development and how they work. The important point made is that children’s musical thinking goes through stages that are qualitatively different. The year 10s are concerned to get to grips with organizing their ideas as well as creating music that is stylistic. This is different from the first stage where interest is in the sensuous quality of sounds and how they can be manipulated and the second where personal expression is sought after along with an awareness of common forms of expression. The final stage, and the one lying beyond where our year 10s are working at, sees a systematic approach and an understanding of ones individual composing voice. I am just about there I would say!
 ibid p.71.