I am having a very hard time coming up with a good way to describe the phenomenon that I am thinking of, but many people will recognize it. I am talking about the kind of singing rhythm that people use when contrasting two different points. Usually it starts on a high note and continues monotonically until the end of the sentence, and then dips slightly. Then, the same thing happens in the second sentence, but with a bigger dip at the end. Usually the first word is "if" and is emphasized heavily. This tune is also often accompanied by a hand gesture where the speaker makes a dipping motion with his thumb. Sometimes, this is done while reading an argument in a text, but other times this is done when the speaker is saying his own words.
"IF we're holding with some random position in this debate, then we have a CONsequence. BUT IIIIIFFF we hold this other position, then the consequence is dif-erent."
Where does this chanting cadence come from, and why is it so prevalent?