I think that's why you would play her/it "like" one of their French horns. Like as in the movie Rose is English and tells Jack to draw her LIKE she's one of his French girls cause she's not one. You wouldn't say this chicken tastes like chicken...the joke would be redundant if it was a French horn. This picture requires some deeper thought.
That being said it's not really funny.
Maybe she's saying it to a renowned French Horn player whom she is attracted to to play her as well as he plays french horn. Im done figuring out what a imaginary/unfunny post says now though.