misses the main point of compositional theory, the motive of the composer.
Yet these principles or "rules" can only provide an abstract insight into the composer's Means (i.e. his specific technical articulations) that identify each individual Opportunity (i.e. each specific recorded instance of triad notation). No such model can explore a composer's actual reason or Motive for realizing an opportunity in the way he did.
He then goes on to try to prove that their statistical method is bad, but he makes a big mistake of sampling, trying to compare the results of a 10 chord pair sample with those of a 3,603 sample size. von Hippel and Aarden handle this issue thoroughly in their response to Wibberley, so I will instead focus on his more intriguing statement, that of the purpose for a compositional model.
Wibberley lays out three attributes for a meaningul compositional model: motive, means and opportunity. The means identifies the techniques that can be used, the opportunity looks at the possible uses of the techniques, and the motive examines why the composer chooses a particular technique. Up to this point, I am in total agreement with him, with the caveat that not every good model will cover all three attributes thoroughly. Some models will detail all the possible ways to move from one chord to the next (the opportunities) and illustrate which ways were used by composers (the means) in a given style/genre/period. These models are more general, meant to cover a whole musical language. Other models are very specific, looking at the means used by one composer or the means used by many composers when faced with a specific context. These specific models will focus primarily on the composer's motives. These specific models rely upon the work of the general models, either internally or externally.
But in Wibberley's third paragraph, he claims that motive is all that matters, that means and opportunity are not important.
What I am suggesting is that a composer's choice of note doubling or chord spacing (or anything else for that matter) was never made simply in order to follow established rules and procedures. Rather each choice was made only because it was a composer's "preferred solution" that was deemed at that moment to be aesthetically and artistically the best available. As soon as musical practice is described in terms of "rules" we immediately step away from the language of the musician and become engaged with that of the theorist. What therefore begins life as an artistic musical expression then simply ends up trapped in the world of "theorist-speak".(1) [the footnote assures the reader that "theorist-speak" not meant to be pejorative but rather as a distinction between theoria and practica.]
I first object to the suggestion that theorists are not musicians, though in fairness Roger is probably using "musician" as shorthand to signify performers and composers. But more importantly, Roger makes the mistake of thinking that models detail proscriptive rules. Models are meant to be descriptive, defining compositional languages in the general and the specific. If a composer makes a surprising progression or voice-leading, we can only call it surprising if we know what expected practice is. And general models tell us what expected practice is.
Theorists sometimes get carried away with the creation of partwriting rules or counterpoint species, forgetting that these pedagogical techniques are meant to model normative compositional behavior. These theorists (or theory teachers, more likely) drill partwriting into their students, marking off every instance of parallel fifths or voice overlap that occur in both exercises and music literature. But most theorists (and many theory teachers) realize that the goals of theoretical models are to give musicians the tools to describe both expected and surprising behavior in compositional practice.