When Tori Amos makes up her mind to do something, it's always all-in and there'll be no deterrent. "Any time you get an opportunity to put something out, I'm in the mind that you seize the project with both hands," she says of her boxed set, 'A Piano: The Collection,' due Sept. 26 via Rhino. "And I'm not one to give the record company my blessing and do what [they] think is best. I don't think that anybody knows what's best except the composer or the midwives of the songs themselves."

Inspired by Led Zeppelin's 'Complete Studio Recordings' collection, Amos mined her vaults for an 86-song, five-disc set that chronicles the piano provocateur's near 16-year solo career. "I had access to all the material since 1990, and my goal was to try and retain the integrity of everything," she says. " When you're putting together a work of this magnitude, [the songs] all have to work together. I wanted to have some kind of story -- a payoff denouement for each record."

'A Piano' runs the gamut from Amos' quirky humor as she kicks off the never-before-heard intro jam to 'Marys of the Sea' with her best Juvenile throwback, singing "Back that ass up," to the characteristically cryptic, as with the previously unreleased 'Zero Point.' That track Amos says was inspired by Zecharia Sitchin's 'Earth Chronicles' series, which concerns the writings of the ancient Sumerians and their ideas regarding time. "It talks about Rome ending -- B.C. and then A.D. -- and the idea of what was supposed to happen at zero point," she explains. "I found there to be a strange correlation between America being the super power that it is and Rome being the super power that it was, and what comes along with that kind of power... how you can really forget the responsibility that you have to humanity. The ego becomes bigger than spirituality."

Another unreleased song, 'Take Me with You,' was 16 years in the making, having been rediscovered by her engineer and husband, Mark Hawley. "When we put it up on the boards they looked at me and said, "Well, all it needs is a vocal.' I said, 'I can't do that 16 years later,'" Amos recalls. "I thought about it and the song really started to call me to it. After 48 hours, I could finally finish the lyric and record it."

For a woman who typically minds no rules musically, Amos did set forth one this time around. "There were no remixes allowed to the first two records. That was my law. It's not a democracy. Well, it is 'til it isn't. When it comes to my world, I have to answer to the songs."