Noun
The act of modulating, or the state of being modulated; as, the modulation of the voice.
Sound modulated; melody.
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.
Source: Webster's dictionaryI believe the term modulation denotes in music the uninterrupted shift from one key to another: I do not know the term for change of rhythm without change of measure. Allen Tate
I am much obliged to you for your last letter, and the lessons reed, before. I think I now begin to see a little into the nature of modulation and the introduction of flats and sharps ; and when we meet you shall hear me play extempore.. Thomas Gainsborough
2. In a facsimile transmitter, a device that changes the signal modulation from amplitude modulation (AM) to frequency-shift keying (FSK). Source: Internet
According to incremental expanse of intelligent receivers, automatic modulation recognition becomes a challenging topic in telecommunication systems and computer engineering. Source: Internet
A "Class D" amplifier uses some form of pulse-width modulation to control the output devices; the conduction angle of each device is no longer related directly to the input signal but instead varies in pulse width. Source: Internet
A choice of audio codec, modulation and error-correction coding schemes and first trial broadcasts were made in 1990. Source: Internet