The discourse function of intonation analyzes sentences’ occurrence in the larger contexts.
For example, let’s take a look at the following sentences:
Have you got free time this morning?
I might have later on if that meeting’s off.
They were talking about putting it later.
You can’t be sure.
Each of the four sentences can be studied in isolation and analyzed in terms of grammatical structure, lexical content and so on. But it is clear that these sentences are part of a larger conversation between two people. Usually, in such situations, the meaning of a sentence can be understood only if the preceded conversation is known.
When it comes to the study of intonation in relation to discourse, we identify two main areas:
In the case of attention focusing, the placing of tonic stress on the proper syllable on a particular word in the tone–unit is the most obvious use. In many cases, the tonic stress is placed on the word that is the most important (example: I went to \Thailand).
Sometimes, describing the tonic stress placement according to information content seems to be more appropriate. If a word’s occurrence in a given sentence is more predictable then the information content of that word is lower too. Tonic stress tends to be placed on the words with higher information content.
I have to take the \dog for a walk.
I have to take the dog to the \vet.
Obviously, the word "vet" is less predictable so it has higher information content than the word "walk". However, there are many cases when it is very difficult to figure out which word is more important or has more information content; therefore, the placement of the tonic stress based on these criteria is practically impossible.
Another way in which intonation can assist in focusing attention is the tone chosen. Let’s take a look at the following example:
| Since the \/last time we met | when we had that huge \/dinner | I’ve been on a \diet |
The first two tone units, present information that is relevant to what the speaker is saying but which is not something new to the listener. The final tone-unit presents new information. It is said that falling tone indicates new information while rising tone (or falling-rising) indicates given information.
Intonation is quite important in conversational interaction of two or more speakers. There isn’t much study on this and the study that is done had been done on conversational interaction of a rather restricted kind (between doctor and patient, teacher and pupil etc.) In such material it is relatively easy to identify what each speaker "is doing" in speaking (questioning, challenging, advising etc.)
So, speakers use different prosodic components to indicate to others that they have finished speaking, that the other person is expected to speak, that a particular kind of response is expected, etc.
It seems that all other functions of intonation (attitudinal, accentual, and grammatical) could be seen as different aspects of discourse function.
Some may consider that the discourse approach is useless but even if it is, at least it has shown that how inadequate is to analyze the function of intonation based on an isolated sentence, removed from it linguistic situational context.