can you tell if a piano is out of tune? I'm curious since I don't know anyone with aphantasia. Can you tell if someone is playing your composition correctly?

Yes I can.

That's also the reason why I can compose at all. The analogy would be like: I don't know how pink color is named, but I can say it's pretty.

And on the output: I don't know what colors I used, but the image is pretty.

Only my music teacher tried to play and I knew it didn't work well. It's a peculiar thing.

It's possible to tell from one note. The reason is that the unisons will be out of tune with one another and change the tone quality.