As regards memory, the brain responds best to repeated patterns, such as the melodic and rhythmic patterns of music.
Given That ...
Music aids memory and that Jokes, like music, elicit an emotional response
Why is it That ...
Jokes are usually very difficult to remember.
Evaluate
When we're doing Fill in the Blank (aka Logical Completion), we check to see whether the word prefacing the blank is expecting a Conclusion or a Supporting claim.
The blank is prefaced by SINCE, and since/because always indicate supporting claims. That means this could be Strengthen or Paradox, depending on whether we're supporting a Conclusion or a Surprising Idea, respectively.
Because the previous claim begins with HOWEVER, we know we're supporting some Surprising Idea.
Goal
We need a distinction between music and jokes that will allow us to explain how even though music/jokes are similar on one level, there's a reason why music aids memory and jokes don't.