To be aware of which horn was present when and where, sheds light on several horns that may have been Leutgeb’s. But it is also important to know if these horns differ in their conception from the « regular » French instrument of the XIXth century, and if they do, to what extend these differences in horn manufacture have an impact on the sound.
Today, the regular yellow brass metal (laiton) most of the horns are made of contains 70% of copper and 30% of zinc. But until the XIXth century, when the extraction of zinc was not as easy as nowadays, yellow brass was made of copper and calamine. Also, during the XVIIIth century it was common to have instruments made of 100% copper. Silver instruments were rare due to the difficulties to work such a metal1.
We do know the effect of having more copper in the alloy : in the modern time we call it « goldmessing » and the alloy is around 80% copper and 20% zinc. Goldmessing produces a rather darker, mellow sound ; we can imagine how a horn made entirely of copper would sound. Unfortunately, I am unable to tell how the use of calamine would impact the playing.
Furthermore, De Pontécoulant wrote about the horn player Lebrun, saying that around 1807 he had been able to improve the instrument by altering the thickness of the metal2 ; but I do not know in which way. Did he make it thiner or thicker ? A question I was not able to answer yet. But it seems that there was indeed a difference of thickness between XVIIIth and XIXth century horns.
I had been wondering if horns had lacquer back in the days ; a vernished horn may not sound the same as an unvernished horn. In one of his articles from the Galpin Society Journal, Horace Fitzpatrick wrote :
" Shaving was the eighteenth-century method of finishing brass instruments
by scraping the surface lightly with a sharp knife of triangular cross-section.
Abrasive cloth was not known until the early I800’s. Goldsmith's polish would
have no effect upon the tough black oxide formed by repeated heating, but
skilful shaving could produce a velvety sheen. Further polishing was the
province of the court orchestra lackey- factotum (Kalkant) who was armed
with pumice, chalk, oil, and much cloth. Shaving marks are useful in dating
instruments as the process had disappeared by 18203."
It seems that before the beginning of the XIXth century, horns were given a polished aspect by what Fitzpatrick calls shaving (brossage in French), but lacquer was not used.
Tuckwell do writes that the three Cors Solos made by Raoux in 1781 for Türrschmidt, Palsa and Punto were « beautifully finished with lacquered bells4 » ; but he may be referring to the fact that they were made of silver and thus shiny. In any case, he describes it as a very uncommon thing, which only support what is said above.
Whether lacquer has an effect on the sound of the horn and the way it feels or not is a rather counterversional subject. It is generally said among people who believe there is a difference that the unlacquered instrument has more harmonics (overtones around one note), a more free vibration ; the lacquer makes it brighter and clearer. If difference there is, it is plausible to say that the first option would be the one heard in the time of Mozart.