This mechanism will add two resonance keys to the lower part of your instrument. A thumb key lever next to the thumb rest will allow you to open the resonance keys as you see fit. When pressed they will raise the pitch of the E or F. Otherwise everything will play the way you are used to. This mechanism is lighter and allows you to choose when to raise the pitch or not. The keys can be removed and the tone holes closed with bumpers if needed. This allows you to play in tune when it is critical. We call it the democratic solution.
Thump operated low E/F correction mechanic on an A clarinet.