When was the English horn invented?

The English horn was not invented, but rather evolved from the oboe.

Here's a breakdown:

* 17th century: The oboe, as we know it, was developed in the 17th century.

* 18th century: Around the 18th century, oboe makers started experimenting with longer oboes with a wider bore, which produced a lower, mellower sound. This instrument became known as the cor anglais (French for "English horn").

* 19th century: The term "English horn" gained more popularity in the 19th century.

So, while there isn't a specific "invention" date, the English horn's development can be traced back to the 18th century.