Discursive functions are seldom expressed in an absolutely neutral way. In most cases, various colorings - expressive, affective or social - are superimposed on the utterance by which a function is conveyed. In so far as these colorings are not random shades, but can be regarded as graded nuances within given ranges, selected in order to fit the atmosphere one wishes to create, the term "modulation" seems appropriate to refer to the passage from one nuance to the other, and in particular, from a neutral to a more or less marked realization of the function concerned. Modulation is distinguished from modalization: while the latter modifies the propositional content of an utterance, and may be used as a modulating device, modulation bears on an utterance's illocutionary force. Criteria affecting the realization of a given utterance are described, including the hierarchical and intimate relationships between the participants, the speaker's and hearer's idiolects, and the linguistic environments in which the realization of the function appears. Examples of utterances affected by the mechanisms of modulation are provided. (Author/CLK)