Hibike! Euphonium Specials Episode 7

What’s a transposing instrument?! (移調楽器って何だチュー！) is the seventh and final OVA episode of the first season of the Hibike! Euphonium anime series. It was broadcasted on December 16, 2015.

Synopsis
Hazuki asks Kumiko and Midori what a transposing instrument is. They try to explain to Hazuki, but Hazuki still can't conceptualize any of the information, even when Reina demonstrates.