"This hasn't just been something in the back of our minds, we've really tried to make this something special," says Mac. "It was important to get it right, because you only have six songs. It was important to put the right ones out and in the right way."
Re-works of three of Six60's most-loved anthems make the cut - Rest Of You, Run For It and Forever. But the new, never-before recorded Home is likely to excite fans most.
"We've actually been playing it at live shows since last summer. We've been developing it to a stage where we feel comfortable releasing it and I imagine it will be developed even more by the time it goes on the album, which is exciting because fans can actually get a glimpse into how a song can evolve," says Mac, hinting at what's in store on the band's work-in-progress second album.
They've also included Someone To Be Around. "It's an old song that was never really given album treatment or air time. We've always really enjoyed playing that song live and know our fans have really enjoyed it as well," says Fraser.
Perhaps more intriguing is the band's choice of a cover - TLC's 90s R 'n' B hit Waterfalls.
"Honestly, thinking about it now, it's super-sur-prising we're doing it," laughs Mac.
"We had this big discussion because we knew we wanted to do a cover but trying to find the right one was really difficult because we're all from such different musical backgrounds. So everyone was throwing songs out there.
"There were heavy metal songs, punk songs, folk songs. Name an artist and we probably pitched the idea. Then someone, probably Matiu because it's way more up his alley, threw out the idea of Waterfalls. Everyone went: that's a really cool song. Everyone knows it; everyone has got a memory of it. It's just a bloody cool song."
And with that, Mac and Fraser are back to work. Six60 didn't just rock up to Roundhead to jam. They'll be here until the early hours of the morning, or until these six exclusive re-worked songs are just so.
Six60's iTunes Session - which has already gone to No 1 on presales - will be available for download on Friday, December 20.
Six60 are performing at BW Campgrounds on Friday, December 27.