modulate

(verb) change the key of, in music. Example: "Modulate the melody."

(verb) vary the pitch of one's speech. Synonyms: tone, inflect.

(verb) fix or adjust the time, amount, degree, or rate of. Synonyms: regulate. Examples: "Regulate the temperature." "Modulate the pitch."

(verb) adjust the pitch, tone, or volume of.

(verb) vary the frequency, amplitude, phase, or other characteristic of (electromagnetic waves).