Samorost 3

I am completely stuck in Samorost 3 after finishing the second planet. I got the key, and according to the a video playthrough I need to use it inside the comet.
See here https://youtu.be/svMgDajMxTI?t=233, to see the trumpet used to open the anthill type hole.
And here https://youtu.be/ByeZWnT3U8o?t=1338, to see the guy enter with the key, and use it.

But when I use the trumpet on the hole, nothing happens. I am not sure if the trumpet has any sort of mechanics. Do you have to charge it with a particular song first?

I went there before the other island and got in without the key and opened it. I'm working on getting the key now. I can't imagine the order should matter.

I am wondering then, if used any save games? And had any with the hole open?