I'm not sure if I believe in the existence of a solar-powered harmonica. Don't you just blow into it?But just in case your instrument is not what I'm picturing -- watch out for Europeans who have no idea of how hot temperatures become in other parts of the world. North Europeans are used to mild temperatures. They can get all excited when the temperature goes over 80 F.
For example, I was reading a library book about hellebores (garden flowers) which said that they can easily handle hot summer weather, such as temperatures in the 80's. Right away I knew I had borrowed an English book.
I have planted some hellebores and mulched them. We are going to see how they handle temperatures of 105.
Moral: if you are reading the manual for a solar instrument, check to see how hot it can safely get.