Two albums in, the members of Slash's band have settled into their groove.

"We had a certain kind of chemistry, right from the get-go," say Slash, whose World On Fire album featuring Myles Kennedy and The Conspirators, out today, is streaming at USA TODAY. "From all the touring and the constant playing and writing together, everybody has hit their comfort zone as a unit."

The follow-up to 2012's Apocalyptic Love, World On Fire features the guitarist, Alter Bridge vocalist Kennedy and a rhythm section consisting of drummer Brent Fitz and bassist Todd Kerns. The title track, No. 6 on USA TODAY's active rock airplay chart, sets the tone for the album.

"There's a heaviness to the record that is similar to World On Fire," Slash says. "It's a very diverse record. It's all rock 'n' roll, but it covers different feels and rhythms. Across the board, though, it has a certain aggressive quality."

Fans of the classic Slash guitar sound from his days with Guns N' Roses and Velvet Revolver will hear that quality in the riffs that form the foundation of songs such as Wicked Stone, Too Far Gone and The Dissident.

"I'm a riff guy," Slash says. "Even as a kid, way before I started playing guitar, I always gravitated toward songs that had a cool guitar or piano riff, some sort of instrumental melody. I remember it especially with Stevie Wonder, where his songs had a certain kind of groove, a single-note pattern that set up the bed for the rest of the song."

Slash often started the album's songs with a riff, perhaps adding the musical basis for verses and a bridge or a chorus, before bringing them to the rest of the band for input and lyrics from Kennedy.

World On Fire includes one instrumental, Safari Inn, that grew out of a riff that never got lyrics. "I just started playing guitar solos over it; it seemed to be the nature of that piece," Slash says. "It was open to Myles' interpretation. He never really came up with anything for it, so I just shortened it and turned it into an instrumental."

Slash and The Conspirators played the single World On Fire this summer on the Let Rock Rule world tour with Aerosmith. During headlining shows between those dates, they'd usually add Stone Blind and 30 Years to Life.

"I knew 30 Years to Life would end up being a single at some point," Slash says. "It's an easy song to play, but it's a fun song. It seemed like something we could get together, because we didn't have a lot of time to rehearse.

"Stone Blind, again, was a simple song with a good groove that the crowd would probably get without having ever heard the record."

Now that the album's out, they'll start adding more songs, especially on the European tour that begins in November.

"By the end of next summer, we'll have played every song on the record once or twice," Slash says. "You just keep snapping them off and sticking them in the set."

Slash also has written the theme music for Universal Studio Hollywood's annual Halloween Horror Nights maze, which is set in a dilapidated roadside attraction called Sweet Licks Frozen Clown Pops Family Amusement Center that is run by a family of psychotic clowns.

"Clown music has a certain rhythm to it, a ¾-timing, and a certain sway that you recognize," Slash says. "I took that and came up with a cool melodic riff that fit that and some other little melodies to go with it. It's a theme that runs through the whole thing, but it has different dynamics as you go through different sections of the maze. I'm very proud of it."

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