Chromatic, direct, and “truck driver” modulation (key changes in pop)

Three families of modulation “without a diatonic pivot chord”

Direct (or phrase modulation): the new key begins at the start of a phrase, without preparation. The change is abrupt.
Chromatic: one or more voices move by semitone (chromatic inflection), transforming a chord of the old key into a chord of the new key.
Common-tone: a single held note connects two chords of distant keys (often chromatic mediants).

End of phrase in C (cadence on C), new phrase in Eb (straight to Eb).
It works best if the new key is close (relative, dominant) or if the change is obvious and intentional (final chorus).
The “truck driver’s gear change”: the last chorus goes up by a semitone or a whole tone without preparation, like a trucker shifting gears. Examples:
Michael Jackson, Man in the Mirror (1988): from G to Ab.
Whitney Houston, I Will Always Love You (1992): after the pause and the drum hit, from A to B.
Beyoncé, Love on Top (2011): four consecutive upward key changes in the finale.
Bon Jovi, Livin’ on a Prayer (1986): the last chorus goes up a minor third.

A voice rises or falls by a semitone and changes the function of the chord.

C → C7 → F: the voice C → B → Bb makes C the dominant of F (chromatic inflection).
C → Cm → Ab: C (I) → Cm (P) → Ab: with two inflections you reach a distant key (bVI).
C → A7 → Dm with C → C#: tonicization or modulation toward D minor.
Am → A → D: the Picardy third (C → C#) turns the minor tonic into the V of D.

C major (C E G) → E major (E G# B): the common note E stays, the others move by a semitone. Very little material, big effect.
C → Ab (common note C): typical of Schubert and of soundtracks.
You can also hold a single note (unison, ostinato) and change everything underneath.

To go up a semitone (from C to Db) the dominant of the new key is Ab7: C – Ab7 – Db (Ab7 = German sixth of C, enharmonic).

Going up too far: the voice leaves its comfortable register. Check the range (the final chorus + a whole step).
Using it as a “trick” for lack of ideas: in recent pop music it has become less frequent precisely because it is associated with the 1980s–90s.

Take an 8-bar chorus in C.
Version A: repeat it identically a whole step higher (D) after a 1-bar drum fill.
Version B: before the chorus insert A7 (2 beats) and then the chorus in D.
Version C: Ab7 and the chorus in Db. Compare the energy and “naturalness” of the three.

Modulation techniques (basic lesson), enharmonic modulation, chromatic mediants, tonicization, contemporary pop forms.