Direct modulation and abrupt key change
The simplest modulation is direct: stop the current key and start a new one, often announced by a hit on an unprepared chord. Modulation from C major to G major happens by jumping directly to the new key, often with a drum fill or synth stab marking the moment. This bold approach works in pop and dance music where the contrast is the entire point.
Direct modulation is popular in modern music production (especially electronic) because it does not require harmonic setup or resolution. A key change from verse to chorus simply happens, and the ear accepts it because no competing harmonic context says otherwise.
Pivot-chord and chromatic transitions
A pivot-chord modulation uses a chord that naturally belongs to both the old and new key. If you are leaving C major for F major, the C major chord is native to both, so you can pivot through it. This smooth transition is favored in classical music and jazz, where the modulation happens so seamlessly that listeners feel the arrival without noticing the mechanism.
Chromatic modulation uses chromatic motion (half steps) to slide from one key center to another. A descending chromatic bass line moving from C to G creates a gravitational shift toward G while retaining some harmonic ambiguity. This technique appears in everything from The Beatles to modern R and B.