Over at Paste Magazine Troy Sanders the basist for Mastodon related how they do their songwriting process.
"Since day one, we’ve always written albums thinking the music was the score of a movie," Sanders said. “Then we’ll create the lyrics or story line on top of that, as if we’re writing the dialogue to match the movie’s cinematography"
How they got asked to do the score for Jonah Hex was out of the blue, seems director Jimmy Hayward is a fan and liked their album Blood Mountain.
And just after their tour ended with Metalica they recieved a call from Hayward asking them to do the score.
Sanders recalled "The movie budget covered our studio fees, but it was a break even deal," “Malkovich, Brolin and Megan Fox all took pay cuts to be a part of this movie—that alone speaks volumes about how much people care about this film.”I guarantee an incredibly popular misconception will be, ‘Oh my god, they’re selling out doing a [frick]ing comic-book movie. They probably got a huge paycheck and don’t give a shit about integrity,’” Sanders continued. “The fact is the exact opposite. We sacrificed another two weeks away from home to give away an album’s worth of material for nothing in return but satisfaction in being a part of something incredible.”
On a side note Mastodon's guitarist Brent Hinds gets a cameo in the film,
he's one of the first of a 172 unfortunate souls to be killed
