During speech people tend to single out from an utterance stretch only some of its elements while others are more or less overlooked as insignificant. The reason for it is that some elements of the speech chain stand out phonetically and functionally among the others, i.e. they are prominent, or stressed. Prominent segments are usually associated with a pitch change or a pitch contrast of some kind combined with increased force of articulation, or loudness, and increased duration. Such a cooperation of different prosodic parameters is reflected in the notion of the tone ó the basic element of the prosodic system of English.
According to the way of their producing, tones are divided into two broad classes:
1. static (called by R. Kingdon) or level tones ó tones of unvarying pitch (are produced by keeping the vocal cords at a constant tension)
2. kinetic (called by R. Kingdon) or dynamic tones ó tones of varying pitch (are produced by varying the tension of the vocal cords)
According to the actual height within the speakerís voice-range static tones may be high, mid and low with further gradations within each type (the number of static tones corresponds to the number of perceptible pitch gradations, or levels).
Kinetic tones are generally classified according to the following criteria:
1. direction of the pitch change;
2. width of the pitch change, or its interval;
3. relative position of the pitch change within the speakerís voice-range.
The number of kinetic tones types corresponds to the number of directional types of pitch-change, whereas variations in the width of the pitch-change and its register are responsible for further subdivision of each of the tone types into subtypes (variants). The general classification of English kinetic tones:
1. Fall (High Narrow, High Wide, Mid Narrow, Mid Wide, Low Narrow, Low Wide);
4. Rise-Fall (High Narrow, High Wide, Low Narrow, Low Wide).
Static and kinetic tones differ both in form and in their function in speech.
Static tones give prominence to words. The degree of prominence is proportional to the pitch-height of the static tone: the higher varieties are usually associated with greater prominence and, consequently, greater semantic importance.
Kinetic tones not only give prominence to a word, but also indicate the communicative type of an utterance, express the speakerís attitude towards the subject-matter, the listener and the situation and single out the centre of new information in an utterance, i.e. the point of greater semantic importance as viewed by the speaker.
The total number of tones (static and kinetic) in an untterance or any part of it, forming a separate intonation-group, is determined by the number of important (ptominent) words, and most typically, there are from 1 to 5 of them.
Not all stressed syllables are of equal importance. One of the syllables has the greater prominence than the others and forms the nucleus, or focal point of an intonation pattern. Formally nucleus may be described as a strongly stressed syllable which is generally the last strongly accented syllable of an intonation pattern and which marks a significant change of pitch direction, that is where the pitch goes distinctly up or down. The kinetic tone carried by the nucleus is called the nuclear tone. The nuclear tone may be called terminal, since it is always the last kinetic tone in an intonation-group and serves as its boundary marker. Terminal tone is a change of pitch at the junction of two sense-groups or untterances, it is formed by the nucleus and the tail.
The term tone should be distinguished from the term tune, which is used to refer to the pitch pattern of the whole intonation-group. The notion of tune is wider, because the tune may include several tones while a tune of a minimal size can coincide with a kinetic tone (in a monosyllabic utterance, e.g.: No. Well.)
Unstressed or partially stressed syllables which precede the first full stress (the onset) form the prehead. The syllables (stressed and unstressed) from the first stressed syllable up to, but not including, the nuclear syllable form the head. Unstressed or partially stressed sellables following the nucleus are called the tail.