The way pitch is used linguistically differs from language to language. In English, it does not much matter whether you say cat with a high pitch or a low pitch. It will still mean 'cat'. However, if you say [ba] with a high pitch in Nupe (a language spoken in Nigeria), it will mean 'to be sour', whereas if you say [ba] with a low pitch, it will mean 'to count'. Languages that use the pitch of individual syllables to contrast meanings are called tone languages.
Most of the languages in the world ate tone languages. There are more than 100 tone language in Africa alone; many languages of Asia, such as Chinese, Thai, and Brumese, are tone languages, as are many Native American languages.
Thai is a language that has contrasting pitch, or tones. The same string of 'segmental' sounds represented by [naa] will mean different things when spoken with a low pitch, a mid pitch, a high pitch, a falling pitch fromm high to low, or a rising pitch from low to high. Thai therefore has five tones :
In Akan sometimes called Twi, the major language of Gana, two tones are used for contrast in two-syllable words :
In some tone languages the pitch of each tone is 'level'; in others, the direction of the pitch (whether it glides from high to low, or low to high) is important, Tones that 'glide' are called contour tones; tones that do not are called level or register tones. The contour tones of Thai are represented by using a high tone followed by a low tone for a falling glide, and a low followed by a high for a rising tone.
In a tone language it is not the absolute pitch of the syllables that is important but the relations among the pitches of different syllables. After all, some individual speakers have high-pitched voices, other low-pitched, and others medium-pitched. In many tone languages we find a falling-off of the pitch, or a 'downdrifting'. In the following sentence in Twi, the relative pitch rather than the absolute pitch is important :
The lowering of the pitch is called downdrift. In languages with downdrift and any tone languages in Africa are downdrif languages a high tone that occurs after a low tone, or a low tone after a high tone, is lower in pitch than the preceding similarly marked tone. Notice that the first high in the sentence is given a pitch value 7. The next high tone (which occurs after an intervening low tone) is 6; that is, it is lower in pitch that the first high tone.
This example shows that in analysing tones, just as in analysing segnents, all the physical properties need not be considered; only essential features are important in language in this case, whether the one is 'high' or 'low' in relation to the other pitches, but not the specific pitch of that tone.
Languagea that are not tone languages, such as English, are called intonation languages. The pitch contour of the utterance varies, but in an intonation language, as opposed to a tone language, pitch is not used to distinguish words from each other.
