https://en.m.wikipedia.org/wiki/Carlos_Sanchez-Gutierrez

https://en.m.wikipedia.org/wiki/Circle_of_fifths

The cor anglais (UK: /ˌkɔːr ˈɒŋɡleɪ/, US: /ˌkɔːr ɑːŋˈɡleɪ/^[1][2] or original French: [kɔʁ ɑ̃ɡlɛ];^[3] plural: cors anglais) or English horn in North America, is a double-reed woodwind instrument in the oboe family. It is approximately one and a half times the length of an oboe.

Cor anglais or English horn

Woodwind instrument
Classification	Woodwind Wind Aerophone
Hornbostel–Sachs classification	422.112-71 (Double reed aerophone withkeys)
Developed	about 1720 from the oboe da caccia
Playing range
Written pitch, notated in F, sounds a perfect fifth lower Sounding pitch
Related instruments
Piccolo oboe Oboe Oboe d’amore Oboe da caccia Bass oboe Heckelphone Contrabass oboe

The cor anglais is a transposing instrument pitched in F, a perfect fifth lower than theoboe (a C instrument). This means that music for the cor anglais is written a perfect fifth higher than the instrument actually sounds. The fingering and playing technique used for the cor anglais are essentially the same as those of the oboe and oboists typically double on the cor anglais when required. The cor anglais normally lacks the lowest B♭ key found on most oboes and so its sounding range stretches from E₃ (written B♮) belowmiddle C to C₆ two octaves above middle C.

https://en.m.wikipedia.org/wiki/Cor_anglais

Alfredo Kraus Trujillo (Spanish pronunciation: [alˈfɾeðo kɾaus tɾuˈxiʎo]; 24 November 1927 – 10 September 1999) was a distinguished Spanish tenor from the Canary islands(known professionally as Alfredo Kraus), particularly known for the artistry he brought toopera‘s bel canto roles. He was also considered an outstanding interpreter of the title role in Massenet‘s opera Werther, and especially of its famous aria, “Pourquoi me réveiller?”

https://en.m.wikipedia.org/wiki/Alfredo_Kraus

Friedrich Adolf Ferdinand, Freiherr von Flotow (27 April 1812 – 24 January 1883) was a German composer. He is chiefly remembered for his opera Martha, which was popular in the 19th century and the early part of the 20th.

Source: Friedrich von Flotow – Wikipedia