Particularly in big band music, a progression may culminate in a climax followed by a short disorganized part (a few bars at most), where everyone "plays what they want". After that phase of chaos the band picks up its tidy work again.
What is the name of this part and how do you indicate it in the score?
I used to think it was called bisbigliando, but I just Googled that and learned that it's some kind of trill.
I don't have a good example at hand, but if you listen to Brian Setzer at 1:50 you may get the idea. It is basically just a long note played somewhat slovenly. It can get a lot more extreme than that.
Rock bands sometimes use a similar technique at the end of a song, followed by the final "bang", like what Cream does here at 6:18. However, the song almost never picks up after the chaotic part, but ends. Not sure if that goes by the same name, does it?
I now remember where I heard it the first time. It was in the book "The professional arranger composer" by Russell Garcia. It comes with a 45 single, containing a song "Force 12". You can see it on Google Books.
He marks the part I mean (page 75) with wavy lines and the word "bisbigliando", thought in the text he puts it in quotes as if it is not the correct name. I can't for the life of me find an audio file containing this song.