modulate

Concise Oxford English Dictionary © 2008 Oxford University Press:
modulate /ˈmɒdjʊleɪt/

▶verb

• 1 exert a modifying influence on; regulate.

• 2 vary the strength, tone, or pitch of (one's voice).

  ■ alter the amplitude or frequency of (an oscillation or signal) in accordance with the variations of a second signal.

• 3 Music change from one key to another.

– derivatives
modulation noun,
modulator noun.

– origin C16 (earlier (ME) as modulation): from L. modulat-, modulari ‘measure, make melody’, from modulus (see modulus).