Modulation /(?)/

Mod·u·la·tion

Modulation

n.
  1. The act of modulating, or the state of being modulated; as, the modulation of the voice.
  2. Sound modulated; melody. [R.]
  3. A change of key, whether transient, or until the music becomes established in the new key; a shifting of the tonality of a piece, so that the harmonies all center upon a new keynote or tonic; the art of transition out of the original key into one nearly related, and so on, it may be, by successive changes, into a key quite remote. There are also sudden and unprepared modulations. (Mus.)
  4. The alteration of hte amplitude, intensity, frequency, or phase (of the carrier wave of a radio signal) at intervals, so as to represent information to be transmitted. (Electronics)