Frein harmonique

Hello,

I’m translating a text from French to English and I’m wondering how to define ‘frein harmonique’, an invention by Gavioli, appreciated by Cavaillé-Coll in order to improve the sound of the gambas. Here is an illustration: http://decouverte.orgue.free.fr/illust/frein_harmonique.png. Can anyone tell me the exact word in English? Thanks in advance.

I believe it's Harmonic Bridge.

Frein translates as "brake" and the type of harmonic bridge found in fairground organ strings is commonly referred to as a harmonic brake in England or in the original French as frein harmonique. It is also referred to as a harmonic bridge or simply as a "beard".
It is uncommon to find the more exaggerated style of bridge used in fairground organs in church instruments and the frein normally consists of a small cylinder of wood or metal pinned in between the ears. Audsley shows several different types including the classic Gavioli type model which all do pretty much the same job of splitting the harmonics and helping prompter speech.
Fairground organ strings are generally made of wood whereas those in the church / concert organ are generally of metal. However, I do have some excellent samples of a Norman & Beard wooden bass and Schulze used them in many of his organs in the same way.

Yes, Frein is brake or bridle, or curb, and it exists only in French. In Spanish and Italian, the same word is "freno." I wouldn't call it a harmonic bridge, as Audsley mentions both in the same paragraph, saying they are distinct. The "harmonic bridge" or "acoustical hopper" are german designs to approximate the same thing, and the "frein" is the French variant, of different engineering. It's on page 473 of the edition of Audsley's "Art of Organbuilding, Volume II." I would leave it untranslated, or call it the "harmonic brake," a literal translation, to distinguish.

In addition to promoting faster speech, they act as a airfoil to delay and speed up the passage of the wind sheet across the upper lip to create more of a square wave versus the sine waveform desirable in flute stops.

A big thanks to all for so many answers. I feel more secure in my translation now. I will reveal to you later the surprise that I am preparing for the community of organists…

I have usually heard this is called a "beard" in the US.

Here is the description from the Organ Supply Catalogue"

On string pipes, beards or rollers are usually provided between the ears to stabilize pipe speech. For
Quintadena pipes or small scale Flute basses, box beards are often provided.