Continuing on the topic of high horn mouthpieces, in recent years I have owned two examples each of the Moosewood BD and Osmun Haydn mouthpieces. These are mouthpieces designed for playing high notes and seem to me to be especially suited acoustically to the high F side of the horn.
Of the BD cup Moosewood states in their website that it is for descant horns and offers “Best response in high register, Baroque performance, chamber music.” It is #20 bore, very small for a horn mouthpiece.
Of the Haydn cup Osmun states in their website that it is “A shallow cup with a pronounced curve in the side wall. Designed to favor the extreme high register.” It is #16 bore, certainly on the small end of the spectrum of standard horn mouthpieces.
As to cup depth, the BD is slightly deeper than the Haydn but this is offset somewhat by the bore being smaller than the Haydn. Sound wise the BD is a little brighter to my ear but only by a degree; they are clearly similar mouthpieces and brighter than any standard horn mouthpiece, with quite a bit shallower cup.
The examples of both used for this testing have European shanks that fit my vintage descant properly.
So what can they do for you?
Either one is clearly better on the high F side of my descant than my standard mouthpiece, an Osmun copy of an old Conn 5BN that I really like (more info here). Trying them back to back either of these mouthpieces works very well on my descant and actually they both work well on my double too. The high range is really better in particular; I would love for it to feel like that all the time!
On the double though, as good as they feel in a way, they really are not the right mouthpiece for general playing. Too bright for the double horn; at volume they would really stick out in any ensemble. For softer, very high playing though either would work fine on a standard double, although they do feel a bit “stiff” to my tastes (in slurs).
A few years ago when I was playing my triple a lot I used the Haydn cup for a while as my main mouthpiece. I think it has potential in the context of a triple, as the typical triple is a heavier horn so it takes out some of the extra edge that the small mouthpiece puts into the sound. It is a topic to consider carefully if you are a triple player or considering becoming one.
And watch the pitch level
On both of these mouthpieces I need to pull out about a half inch more than with my standard mouthpiece. It is due to the smaller cup volume impacting pitch level. By the same token, if you use a very deep cup mouthpiece on any horn the pitch will drop and you will need to push in. In the case of my descant, I actually had the high F side main slide extended a bit for better intonation with the smaller mouthpieces. Depending on your tuning slides you may not be able to get the horn down to pitch with a small mouthpiece of this type.
The big picture
In short, back a couple hundred years ago horn mouthpieces were very deep and optimized acoustically toward the low F horn. With double horns in the 20th century mouthpieces trended toward smaller models that were optimized to the B-flat horn. Today, with the use of the high F side, mouthpieces are a topic to consider carefully if you are a user of horns with a high F side, and in general I believe that mouthpieces will trend toward smaller, more efficient playing models.
To hear the BD mouthpiece in action please check this video of the B-Minor Mass. There are probably other similar mouthpiece models on the market by other makers (feel free to comment below). In short though these are both very nice mouthpieces and a mouthpiece like this should be in the collection of every serious high horn player.