As Anthrax prepare to unleash their long-awaited 'Worship Music' album on Sept. 13, we talked to founding guitarist Scott Ian about the changes that took place both on the disc and within the band itself during the project's extended gestating process.

The story of 'Worship Music' has been well-documented. The album was set for 2009 release with newcomer Dan Nelson on vocals after a split with the band's third (recorded) singer, John Bush.

However, Bush and the band split up before that happened, kicking off a series of events that resulted in classic-era singer Joey Belladonna reuniting with Anthrax to record a revamped version of the album.

In the following exclusive interview with Loudwire, Ian chats about the steps that went into recording and re-recording 'Worship Music' (featuring the first single 'The Devil You Know') and how much of a boost it was to get the call to participate in the 'Big 4' tour with Metallica, Slayer and Megadeth, which rolls into New York's Yankee Stadium on Sept. 14.

Congratulations on the new album, we've been listening to an advance nonstop for about three days now...

Awesome, thank you!

At any point in the process, did you ever fear that it wouldn’t get made?

No, no I can’t say that, because I’m just too tenacious to ever let something like that happen. So, it’s a case of where I don’t really let anything get in my way. If I want something done, it’s gonna get done. I just felt so strongly about this record the whole time, that I knew it was something that was going to happen.

Drummer Charlie Benante said the 'Big 4' tour has been a nice shot in the arm for Anthrax; do you agree?

Yeah, I would say so. It was certainly something that was unexpected, would be the best way to say it. It’s not something that we were ever sitting around waiting to happen. Then, we get the call from Metallica, saying, ‘Do you wanna go have some fun?’ It was really good timing all around, because at that point where we first found out that these shows were gonna happen, we didn’t even have a singer. I think that really was the impetus to get Joey [Belladonna] back in the band, because we felt Joey should be the singer who represents Anthrax on those shows. He was the singer of that era, it just made so much sense.

Then, of course, out of those conversations, it turned into, well, ‘Joey should just be the singer of Anthrax.’ I think once we started going down that road, everything just started to go right for the band, and things started to fast-track at that point. We knew all of the decisions we were making creatively were the right ones, and yeah, a lot of it had to do with the fact that those shows were offered to us.

If there was going to be a ‘Big 5’ tour, who would get your vote to join the bill?

Pantera. Yeah, either them or Sepultura.

Has the music on 'Worship Music' changed much since the version with the other singer?

Some of its changed, some of it’s the same. All the songs were written by Charlie and Frankie and I, so, you know, it’s our record. The only difference is, there’s three or four songs that were pretty much completely rearranged, rewritten and re-recorded from top to bottom. There are also songs from the previous version of the record that didn’t make this album. Then, you know, Joey was pretty much having free reign, if there were things he wanted to sing differently, he was certainly given the freedom to do that.

Did any of the lyrics change?

Well, some of them did, because some of them were years old. I just felt like things needed updating. I had new ideas, we were changing music, so if the vibe of the song changed, it just gave me new ideas. So yeah, certain things changed on every level. I would have to really go back and listen top to bottom and see if anything didn’t change just a little bit even, but truthfully I haven’t had a second to do that.

Compared to the hard-rock leanings of 2003's ‘We’ve Come for You All,’ this new record seems more straight-up thrash. Does that seem fair to say?

Oh, you can say whatever you want. I don’t judge or compare or critique our records. I leave that up to the people that listen to our records.

The track 'In the End' has this big, epic sweep -- what inspired you on that song?

Well, it’s funny, cause it didn’t even start out as that song, it was a completely different song. It’s a song that pretty much took us four years to finish, but we stuck with it because we just felt so strongly about it from the start. At some point, just musically – it works for me the same way, every time – I hear music, and I start hearing words over whatever part of the song.  And from those few words, that'll start giving me an idea of what I’m gonna write about. There was something just so epically big about that song that made me start writing it about [late rockers] Dimebag [Darrell] and Ronnie James Dio.

Click Here for Scott Ian's Thoughts on the Upcoming Loutallica and Van Halen Albums

Watch Anthrax Perform 'Antisocial' at the 'Big 4' show in Bulgaria