We recently watched the Doctor Who episode- A Town Called Mercy which was set in the wild (weird) west. Pretty good episode. The Doctor pulling the iron on the guy was a surprise. The wild west with a cyborg is cool. A bit of a Deadlands feel and maybe a West World homage. The Doctor in a stetson is always a win.
One of the most striking elements of the episode was the musical score, which naturally was drenched in Ennio Morricone themes along the lines of his Sergio Leone film scores.
The band that performed the song was originally named Apple Trees and Tangerines and then changed their name to POWER. Then it appears that they changed their name again to Flint Eastwood (which, as you'll see in a moment, kind of makes sense)
Here's the theme from A Fistful of Dollars. Obviously the whistling... but listen to the guitar at about 2:05 into the theme. It sounds like that bit serves as the foundation for "Can You Save Me/Covert Affairs' theme.