To shift to another key.

Changing from one key to another in a composition.

The change of key in a composition verified by a cadence in the new key (otherwise, it is a passing modulation or touching upon a different key). As a general rule, modulations to the sharp side raises tension, modulation to the flat side lowers it. Modulations to related keys are ideally accomplished by means of 'pivot chords', i.e., a chord which is common to both the initial and the new key (like the submediant chord -vi- followed by II(#) - V when modulating to the dominant; ii-V-I in the new key); or the tonic chord itself would be the subdominant of the dominant key: I - II(#) - V would be a smooth modulation to the dominant (IV-V-I in the new key). Some other means to modulate are: circle-of-fifth progression to modulate to another degree of the scale or one-step sharp or flat, by changing the chord before the new tonic to a dominant seventh if required; changing any chord to a dominant seventh of the new tonic by adding a minor third above a major triad (like - IV would be - I in the subdominant key); in minor keys, the submediant is a major chord, if it is made a dominant seventh and followed by its tonic, this would be modulation to the flattened supertonic; resolving a diminished seventh on the dominant seventh of the new key and progressing to the new tonic (see diminished seventh); using an augmented sixth on the flattened submediant of the target key and resolving onto the new tonic via its dominant (like Ab - G - C) [modulation via outward resolution]; using a Neapolitan sixth to modulate to the flattened submediant (in C major, Db chord as the Neapolitan -IV in Ab- followed by -in Ab- and Ab as the new tonic: IV-V-I in the new key) or by using the Db Neapolitan chord as the dominant of the next key (to Gb). The (major) tonic chord of the prevailing key would be the Neapolitan chord of the new key a semitone lower (in C, bIb - IV - VII would be IVb - V - I in B). This is another use of the Neapolitan chord to modulate a semitone lower. Direct juxtaposition of the new key is not considered to be a modulation by some.