frequency modulated

from The Collaborative International Dictionary of English v.0.48

modulated \modulated\ adj. (Electronics)
   1. Having either amplitude, intensity, frequency, or phase
      altered at intervals to represent information to be
      transmitted; -- of the carrier wave of a radio signal
      transmitted from one device to another for the purpose of
      conveying information. Opposite of {unmodulated}.
      [Narrower terms: {frequency modulated}; {amplitude
      modulated}]
      [WordNet 1.5]

   2. altered in volume as well as tone or pitch.
      [WordNet 1.5]