Definition of "modulate"

(transitive) To regulate, adjust or adapt  examples

(transitive) To change the pitch, intensity or tone of one's voice or of a musical instrument  quotations  examples

(transitive, electronics) to vary the amplitude, frequency or phase of a carrier wave in proportion to the amplitude etc of a source wave (such as speech or music)  examples

(intransitive, music) to move from one key or tonality to another, especially by using a chord progression  examples