Modulate (verb)

1. To change or adjust the frequency, amplitude, phase, or other characteristic of a wave or signal.
2. To vary or inflect the pitch, tone, or intensity of the voice or speech.

Origin:

From the late 16th century word modulate, which comes from the latin word modulatus, which means to measure or to regulate.

Examples:

1. The radio station modulated the signal to avoid interference.
2. The singer modulated her voice to reach the high notes.
3. The musician modulated the key of the song to fit the singer's range.
4. The engineer modulated the power output of the generator.
5. The speaker modulated the tone of his voice to convey emotion.