Taking place during a summer festival is a good setting for the theme but I would like a little more than that such as explanations for instrument choices and whatnot to make the connection even stronger.
The shaker instrument playing the same pattern for the 3 investigations songs can get a little repetitive. Changing it up a little in the song or having it be slightly different for each one would improve the songs IMO since it would help give them each their own identity even more.