Webster's Revised Unabridged Dictionary · 1913

Modulate

Modulate , transitive verb

[Latin modulatus, past participle of modulari to measure, to modulate, from modulus a small measure, meter, melody, dim. of modus. See Mode.]

1.
To form, as sound, to a certain key, or to a certain portion.
2.
To vary or inflect in a natural, customary, or musical manner; as, the organs of speech modulate the voice in reading or speaking.
Could any person so modulate her voice as to deceive so many? — Broome
3.
(Electronics) To alter the amplitude, frequency, phase, or intensity of (the carrier wave of a radio signal) at intervals, so as to represent information to be conveyed by the signal; -- a technique used to convey information by means of radio waves transmitted by one electronic device and received by another.

Modulate , intransitive verb

(Music) To pass from one key into another.