Sometimes in a piece of music there is a portion that sounds totally away from the main tune of the song. Is there a name for that part of the music, or that transition?
In songwriting, this is typically called a "Breakdown" or if it were to have vocals it might be called a "Bridge".
A Bridge will literally bridge a verse to a chorus or even a chorus to a second chorus. Vocally, you might offer a new point of view or new idea.
A Breakdown (which is usually instrumental) diverts away from the main theme in order to refresh your ears and get you ready for another verse or chorus.
My favourite Breakdown is from Sting's "Englishman in New York". It's completely out of place, which works perfectly in the song because an Englishman in New York is literally out of place! Check the song out on YouTube.