What are twists or transitions in a song called?

I'm having a mind blank right now, and can't remember what the word is to describe twists in a song. Like a song going from quiet acoustic, and then kicking in to full-on heavy guitars, and then surprisingly taking on a psychedelic turn, and then smoothly transitioning into some jazz... etc. (just an example) Does anyone know the word?? I think it starts with an "r" but I could be wrong.What are twists or transitions in a song called?
Multiple genre.

california academy of sciences

pro comp