Here are a few highlights from Ch. 3 of Vachek, Josef. 1973. Written Language: General Problems and Problems of English. The Hague: Mouton. Chapter 3 is "Some Consequences of the Functionalist Approach."
"Orthography is, in fact, a set of rules enabling the language user to transpose the spoken utterances into the corresponding written ones, in other words, it is a kind of bridge leading from the spoken norm of language to the written." p. 18.
"The term spelling, in its turn, used in its narrower, more specialized sense, denotes another important device: it serves to express the material make-up of the written utterance by phonic means, i.e. by successively naming each of the graphemes composing that utterance." p. 18.
"The phonetic transcription does not belong to the domain of the written norm, but to that of the spoken -- transcribed utterances present the acoustic make-up of the utterances projected on paper. p. 19.