/
ˈmɒdjʊleɪt/
v.
   - exert a modifying influence on; regulate.
- 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. 
- Music  change from one key to another.
Derivative
- modulation n.
- modulator n.
Etymology
C16 (earlier (ME) as modulation): from L. modulat-, modulari ‘measure, make melody’, from modulus (see modulus).