I have no idea what instrument this is (some sort of traditional English horn?), but it’s definitely meant to poke fun at Hagrid in his out-of-character role. Williams continues to display his virtuosity at adapting a new theme over and over in many new contexts.12. Monster Books and Boggarts!

(Is there a non-traditional English horn?)

I do believe the writer is hearing an English horn. I played music from Harry Potter and there’s a very fun English horn lick. I remember Hagrid’s name in the title.