Modulation
(1) Gradation of sound in intensity. (2) Change of key or tonality.
Diatonic modulation moves from one key to another by means of chords from related keys; chromatic modulation, by means of chords from non-related keys; enharmonic modulation, by substituting # for 2, or the A passing or transient modulation is one followed by a quick return to the original key; the signature is not changed in a modulation of this kind. A final modulation is one in which the new key is retained for some time, or permanently; it is generally indicated by a change of signature following a double bar.