In the present study I am adducing arguments against the assumption that there is a discrete level of grammar where all syntactic operation has stopped and the assignment of phonetic values to the then existing structure (the output of transformations) begins.
The concept of ‘surface structure’ has received the following definitions in Chomsky's various works: ‘a proper bracketing of the linear, temporarily given sequence of elements, with the paired brackets labelled by category names (that is a labelled tree diagram, with such categories as Sentence, Noun Phrase, Verb Phrase, Noun, and a small number of others serving as labels)' (Chomsky, 1966: 21), ‘the organization into categories and phrases that is directly associated with the physical signal’ (Chomsky, 1968:25). These definitions take the physical event of speech as a starting point, and refer to the organization of the sentence on this level (cf. Chomsky, 1965a: 15). One finds, on the other hand, that in the Chomskyan system ‘surface structure’ is also defined in terms of derivation, as the last item in a finite sequence of phrase-markers, the output of the transformations (Chomsky, 1970: 53 f., 87), and such surface structures ‘are mapped into phonetic representations by the phonological rules’ (ibid.: 54) and are assigned intonational contours by rules of phonological interpretation (ibid.: 77). This is summed up in the formula ‘phonology: Pn→phonetic representation’ (ibid.: 87, where Pn is the surface structure, the last phrase-marker).