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As valve tubing warms and cools from the circulation of the warm air, as it cools a slight vacuum is created in the tubing so the next time the valve is pressed it will have a little pull as the pressure is released.

Venting stops this from happening as the tubing is always vented to the outside air. On your horn venting requires drilling a small hole in the rotary valve case between the two pipes of the valve. Many horns come from the factory already vented (Miraphone Firebird, Bel Canto, 129x series and 5050 Euphonium, Meinl Weston 6450, etc.). Venting also allows loose slides to move and tentatively fall out of the horn when placed on the bell as there is no compression in the slide to hold them in place.

I play several rotary valve horns and have not vented them and I don't seem to have this issue. The one question I would ask - Is there a slight sound of a puff of air coming out of the bell before the sound begins? If so your issue is elsewhere.

Happy New Year to you and All my TubeNet friends for a wonderful 2015.

Roger Lewis

Venting would only help if you are moving valve slides while playing. To me, it didn't strike me as the issue at all. It sounds as if you are physically changing your lips with every articulation. A lesson with a highly qualified teacher would be much more helpful.

I'm parked squarely with Roger. My rotary horns are vented because my first horn came that way and to do otherwise is annoying to me. Out of curiosity, what make and model horn do you have? In my experience, the larger the bore the greater the airspace and therefore the larger potential for a benefit re equalizing air pressure.