After a successful summer tour with Kiss, Def Leppard gets back on the horse for a one-off show Saturday in Rancho Mirage, Calif., which will be slightly odd for the group, since Vivian Campbell -- currently getting treatments as he continues to battle cancer -- sits out, with Steve Brown filling in for the moment. But frontman Joe Elliott tells Billboard it's important for the band t honor the commitment.

"We've never been a band that's blown anything out that we're committed to, so we're honoring the show," Elliott explains. "It'll be a little bit weird; it was a bit weird doing the first one with Viv, to be honest, and that was two years after Steve [Clark] passed away. You look over and it's like, 'Hold on, there's this other guy there...' But it'll just be a footnote in Lep history, and everything'll get back to normal, God willing, next year."

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Elliott says Def Leppard is, in fact, gearing up for "a big push" in 2015 that may well include some new music. The group has "15, 16 songs percolating in various, different degrees of being finished," a dozen from writing sessions in February and the rest from May, and Elliott adds that "we could put three of them out tomorrow. The rest of them need a bit of work." And, he says, it's been heartening for the group to be so prolific. "We only set out to write three or four songs in February and we ended up with 12. I'm still trying to figure out how and why. I think one of the whys is we haven't really written since 2007, 2008, so we're backed up, which is great to have that huge backlog of new ideas sitting around. And I think psychologically the fact that we aren't signed to a label, there was no, 'Oh, they're gonna want a ballad. They're gonna want a hit single. They're gonna want this or that,' the usual thing I suppose every artist in the world goes through. We didn't have to think like that. This time we just wrote for ourselves, and all of a sudden we were just spewing out all this stuff. There was just a little more freedom to the way we've written these songs and the way we've approached recording them."

Because of that, Elliott adds, "There's nothing like what you'd really expect. Some of the faster stuff you can say, 'Oh, I can hear Leppard. But there's none of those kind of 80s ballads, let's call them. There's a couple of slow things but nothing like we've done in the past. It's a lot more basic and raw. It's not a complicated record. It's just 10, 12, 15 songs that are pretty much straight to the point."

Campbell was fully part of the process, Elliott says, and he fully expects the guitarist to be on board as the material is finished. "The latest that I'm aware of with Viv, they were harvesting stem cells from him and do whatever they do in a Petry dish with them, and then they were gonna carpet bomb him with chemo for a week and he was gonna be kept in the hospital...Then they're gonna put the stem cells back in and do whatever they do, wave the magic wand and say 'Abracadabra.' Hopefully by the middle of November they're gonna let him out. We were under the impression he would be in the hospital until Christmas, but the last email he sent me, which was about two weeks ago, said, 'It looks like I may be able to get out of here by mid-November."

Elliott adds that he and the other Def Lep members "don't bombard him with emails and phone calls every day going 'How are you doing? How are you doing?' 'cause it's like saying, 'Has your hair grown any longer since yesterday?' It's a slow process, so you're best waiting. He'll contact us when he's got something to say, but it's all fingers crossed and thumbs up and very positive vibes going around -- coming from him, which kind of rubs off, really. It makes us think there's a good outcome for this."

Def Leppard is also part of the upcoming "The Art of McCartney" tribute album, playing "Helen Wheels," while Elliott joined McCartney's band for "High, High, High;" the set is due out Nov. 18. I addition to the Def Lep work, Elliott will be touring with this Mott The Hoople/Mott band the Down N' Outz staring Dec. 5 in Bristol, England, with 10 dates booked through Dec. 18 in Dublin.