Phonostylistics as a branch of phonetics; its linkage with other linguistic disciplines. Extralinguistic factors causing phonetic modifications of speech.

Definition and overall info. Pronunciation styles

The term phonostylistics stands for the phonological processes conditioned by style, i.e. style-sensitive or style-dependent ones. A scale of styles may be set up in a variety of ways, still it is generally encompassed within the extremes of emphatic vs. informal, with formal in between. Emphatic style is well-exemplified by motherese and citation forms, informal styles include casual, colloquial, intimate, while a speech, a lecture, or a job interview are examples of a formal style. For the purposes of clarity, I will refer to a simplified binary distinction between formal vs. informal only.
As far as the informal style is concerned, there exists the whole array of terms in the literature used to refer to approximately the same type of speech: fast, rapid, allegro, casual, connected, informal, real, spontaneous, or conversational. With respect to the primary style-differentiating criteria, the term casual seems to be the most adequate or, indeed, the least narrow or vague. The criteria are: tempo of speech and attention paid to speech. The criteria take on different values depending on the situation in which a speech act takes place (topic, aim, relation to the interlocutor, place of a conversation) and on the individual features of the speaker. Most commonly, exactly those situations do arise which trigger casual speech, i.e. in other words, most often we speak casually. The relationship between the two criteria is inversely proportional: the higher the degree of attention the slower the tempo.
English phoneticians distinguish a greater number of styles of pronunciation, although among them there is no generally accepted classification of pronunciation