What is that change in tune called?

Question

I was listening to this song here.

At 3:49 I find there is something change in tune or tempo,

What is that transformation called? Is there any english term for this?

Answer 1

Instead of letting the song to end in the tonic (Fm) as it seems, the song chromatically ascends to the dominant (C) and recaps the hook (AbBbC Db Bb) in C as (CDE FD).

I didn't hear any tempo change but since the diminuendo phrase ends on a long note and the hook comes back vigorously through a subito glissando, it has the feeling of returning to the original tempo (tempo primo).

To create the effect, you just need to interrupt an ending with the chorus. To accentuate it, set it in a contrasting key.

Answer 2

This is called a modulation, or more informally (as David indicated) a "key change." It repeats some or all of the song as transposed to a new key. It is very common in some styles of music (for instance, gospel music), and usually is used to add excitement or interest to a repeated section. Some songs only have one, but others have multiple modulations. This can result in a melody line far outside the original vocal range, so it requires either a limited original range for the original melody, or a singer with a particularly wide range. Even in the case that the overall tempo doesn't change, modulation to a higher key literally results in a faster pace for the vibrations composing the individual notes.

In modern popular music modulations are most common near the end, usually travel a single whole step higher (at a time), typically repeat the chorus, and rarely return to the original key. In classical music, on the other hand, modulations were common in the middle, were generally in the dominant or subdominant modes (a fifth or fourth up or down) or in the relative minor (three half steps down), often featured a new melody, and typically returned to the original key.

See this link for some good examples in popular music: Can You Take Me Higher?

...and here's how Bach did it: Bach Double Concerto