modulate

Short definition from Wiktionary

Verb

1. 1
   To regulate, adjust or adapt: To change the pitch, intensity or tone of one's voice or of a musical instrument
2. 2
   To regulate, adjust or adapt: to vary the amplitude, frequency or phase of a carrier wave in proportion to the amplitude etc of a source wave (such as speech or music)
3. 3
   To regulate, adjust or adapt: to move from one key or tonality to another, especially by using a chord progression