modulation

(noun) a musical passage moving from one key to another. Synonyms: transition.

(noun) (electronics) the transmission of a signal by using it to vary a carrier wave; changing the carrier's amplitude or frequency or phase.

(noun) rise and fall of the voice pitch. Synonyms: intonation, pitch contour.

(noun) a manner of speaking in which the loudness or pitch or tone of the voice is modified. Synonyms: inflection.

(noun) the act of modifying or adjusting according to due measure and proportion (as with regard to artistic effect).