modulation

Definition (noun): a musical passage moving from one key to another

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

Definition (noun): rise and fall of the voice pitch

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

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