My guess from a very polydialectal background is the Grisons. Granted, Valais German ( Höchstalemannisch ) is pretty close to it, although a written representation of the Walliser pronunciation, especially of the vowels, is extremely difficult. Anyway, the lyrics definitely have nothing to do with Bernese. " Gschwind " can be found everywhere in the Alemannic areas but not in Bern, where it is " gschwing ."
As for Chur, actually, the by far most frequent pronunciation in the German speaking parts of the Grisons is "G huur ", with a very strongly aspirated "g". I have yet to meet a Püntner who can properly pronounce a German " ch ", be it the Swiss German variant (extremely guttural) or any of the two Standard German versions.
Faltrad is pretty close to the truth: " Chuur " is the regular Swiss German pronunciation, whereas "G huur " is what you hear in all of the Grisons, i.e. very often even when native Rumansh speakers speak German. The dividing line between " Ghuur " and " Chuur " is right in the middle of the Rhine bridge between Maienfeld (GR) and Bad Ragaz (SG).
As for the Standard German soft " ch " (after i- or e-like phonemes), which is as guttural and coarse as the other variant in all German speaking Switzerland except Basel, you may notice that the pronunciation in the German speaking parts of the Grisons depends on its position in a word. In words like " wichtig " it may be almost as soft as in Standard German, whereas in "Richard" or " stecha " (=stechen) it may be pretty close to a pure h. My primary school teacher back in the 'fifties, born and grown up in " Ghuur ", always called my class mate, Richard, "Riihard."
@ misr: In Bern, "Merci vilmal" is pronounced "Märssi füu mau."
@ Lorenzi: Right, and in many local dialects of the German speaking speaking Valais, many of those trailing o's are even pronounced like a German "u": "mit do longu wiissu Ohru," as alluded by jj muge.