Kathleen Schlesinger, 1911 Encyclopædia Britannica, Volume 13… (1911)
“ The Holztrompete is in the key of C; the scale is produced by overblowing, whereby the upper partials from the 2nd to the 6th are produced. A single piston placed at a third of the distance from the mouthpiece to the bell gives the notes D and F. Wagner inserted a note in the score concerning the cor anglais for which the part was originally scored, and advised the use of oboe or clarinet to reinforce the latter, the effect intended being that of a powerful natural instrument, unless a wooden instrument with a natural scale be specially made for the part, which would be preferable. ”
