[Nick Coleman]

It’s likely that when you changed “mono” to “stereo”, TextEdit converted the “straight quotes” surrounding the text to “smart quotes”. This will throw an error, because the XML is expecting plain text characters.

Before changing the text from “mono” to “stereo” in TextEdit:

In the Toolbar, go to the menu option Edit>Substitutions and remove the Checkmark next to Smart Quotes.

That should prevent the error.