Re: harmonica

@pmscortana 😂 I go there often myself!
If you've done all three quests, you now "have" the harmonica.
Basically, it allows you to activate the harmonica at any of the cheese fly nests, and take the flies to fire at cheese walls that are close by & block your way.

Many hide golden chests or gnomes & one is for the final boss quest, for which you need to go to the Boss Gate. Unblocking that wall will open up the entrance to the final quest.