In the United States horns with a stopping valve are not common. The most recent recital I gave is probably the first that I actually made much use of my stopping valve (on passages in Alla Caccia by Alan Abbott) and I must say it is just about the best invention ever.
A stopping valve is most commonly seen on single B-flat horns, descant horns, and some triple horns. This photo is a close up of my triple, which is a Paxman compensating triple. The slide for the stop valve is at the top of the valve cluster. It is the same length as a F horn second valve, so it gives you the ½ step of extra tubing you need.
Backing up a second, normally when you play stopped horn for a person with average hands you finger down a half step while closing the bell tightly and use fingerings only on the F horn. This is because when you play stopped on the B-flat horn it raises the pitch for most players roughly ¾ step which renders it unusable. Some custom fingerings can be found that work on the B-flat horn, as I note in this post, but generally the rule of thumb is to play stopped passages on the F horn for better intonation.
If you have a single B-flat horn or a descant there is no low F side to play stopped notes on! So what do you do? You use the stopping valve which adds ½ step of F horn tubing. This valve has two big advantages over stopping on the F horn:
- You can play stopped horn on the B-flat horn which is much more secure and
- If your hands are small and raise the pitch more than a half step you can pull the slide as far as needed to get things to line up perfectly.
Talking to students over the years I know at this point some readers will be confused how this valve works and why it is a neat thing. Wording it a bit differently, you don’t have to transpose the stopped notes, you can use any B-flat horn fingering you want, and, if your stopped notes tend to be a bit sharp due to small hands, you can adjust the stop valve so that every stopped note is in tune.
More accurate with better intonation–what a deal! When you move on from the double horn exclusively explore the use of the stopping valve, it is a great tool for better playing.