MODULATION, in Music, derived from the Latin modulari. This word, in our language, is susceptible of several different significations. It frequently means no more than an air, or a number of musical sounds properly connected and arranged. Thus it answers to what is sometimes understood by the word tune, and likewise expresses the French word chant. But the precise and technical acceptance to which it ought to be confined, is the art of composing melody or harmony agreeably to the laws prescribed by any particular key, rather than of changing the key, or of regularly and legitimately passing from one key to another.