Definition of "Modulation" :

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

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: a manner of speaking in which the loudness or pitch or tone of the voice is modified

noun: rise and fall of the voice pitch

noun: a musical passage moving from one key to another