Phonological theories natural phonology

Beyond this, we again find that there is httle agreement about how to describe pitch accents and boundary tones. Some theories state there are a fixed inventory of these, while some describe them with continuous parameters. The nature of pitch accents and boundary tones is disputed, with some theories describing them as tones or levels while others say their characteristic properly is pitch movement. One prominent theory states that we have an intonational phonology that parallels normal phonology, and as such we have inventories of contrasting units (sometimes called... 

We might well ask why it should be that 1st is chosen as the default rather than /z/ (note that we shouldn t be misguided by the spelling convention here) and this is in fact a prime concern in developing phonological theories, namely that we choose natural rules rather than simply ones that describe the date. 

Donegan, P. j., and Stampe, D. The study of natural phonology. In Current Approaches to Phonological Theory, D. Diimsen, Ed. Indiana University Press, 1979, pp. 126-173. 

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