Ten-gallon hats, spurs that jingle-jangle, blood-spurting gunfights, the occasional scalping, Soundgarden and Radiohead. The first two episodes of HBO's much-hyped Westworld have had plenty of all the traditional Western trappings, and, to the surprise of some viewers, a saloon player piano that plinks out eerie versions of '90s alt-rock classics. It's all part of the mood-setting plan from the team behind the Wild West-themed show, about strangely sentient robots and the horny, blood-lusting humans who pay to kill and bed them.

"All credit goes to showrunner Jonathan Nolan... he came up with that idea, and he was pushing those songs," explains Westworld composer Ramin Djawadi. He's specifically talking about the inclusion of Soundgarden's "Black Hole Sun" and a mind-bending remake of the Rolling Stones' "Paint it Black" in the series premiere, and the taste of Radiohead's "No Surprises" that cameos in Sunday night's (Oct. 9) second episode. "It's been incredibly fun doing those arrangements on the piano in the saloon. It's a little thing in the background that you might pick up on and then you think, 'Hey, wait, that doesn't belong there!' It makes it contemporary and fun."

Djawadi -- who also serves as in-house composer for HBO's other dramatic behemoth, Game of Thrones -- says he was excited to cook up a "big orchestral" arrangement of the Stones classic for the pilot, where we first meet the humans behind the theme park where anything goes. "I liked the idea of using known music to enhance [the scenes] rather than writing my own music," he says, though plenty of his spooky, atmospheric instrumental themes also show up during the show.

"You're using these existing songs to create a level of comfort and repetition,” he says. "It’s all part of the entertainment, and it reminds us that it is a theme park, and it's not not real, because the hosts are so perfect. We don't know who is who and it helps you get lost in this world.” Playing the remixed rock hits helps remind viewers that they're along for the ride in this imaginary world that isn’t in the distant past, but somehow both in the present and future.

Djawadi has composed stirring music for such action flicks as Iron Man and Pacific Rim, as well as TV dramas Prison Break and Person of Interest, but he said coming up with alternate versions of songs you know and love to enhance the knotty plot of Westworld has posed a unique challenge. For instance, the music on the player piano in the bar that typically serves as the guest's first stop in town isn't just a clever diversion, but a metaphor for the relationship between the humans and the "hosts," aka the robots.

"It's kind of the same symbolism, that it's a set up in the same form of the park, where the songs are preset and it's all pre-done and programmed," he says of the nothing-left-to-chance nature of Westworld. "In the first episode, when Teddy is on the train, every time it's another day, and the piano starts up again and it's the same day again. It's a cool idea to use the piano and the music in that kind of a role... [like as] another character."

In addition to the orchestral versions of the recognizable rock songs, Djawadi has created a more electronic, colder score for the scenes that take place in the park's underground control room, where we see the Westworld overlords working on their robots and trying to diagnose their malfunctions. "What I realized is that because we have the whole Western theme element, we have to score the park and the underground [control room] differently," he explains. "But the piano is the instrument that crosses over well into both worlds, in an organic and electronic way."

Djawadi was sworn to secrecy about what other songs we might hear in future episodes, but he promises that the mix will continue to surprise and delight.