Tom Petty’s widow said there's more archive material to follow the upcoming An American Treasure box set, which arrives on Sept. 28.

She added that the intention behind the releases was to share unheard music for those who want to enjoy it.

“It was not an easy process for any of us,” Dana Petty told Billboard in a new interview. “It was very emotional, and, especially at first, hearing the songs was brutal. But music is healing. It got easier. It felt like Tommy would be so proud of this.”

Confirming that more releases would follow the new box, she noted that “there’s so much more in the vault, so much more that we tried to put on this record, that everyone needs to hear. I just don’t want them to think we’re greedy, because it’s not about the money – it’s about getting the stuff out there for the world to love.”

The 60-song An American Treasure set took form over the course of the seven months following Petty’s death in October 2017. It was curated by Dana alongside daughter Adria, Petty’s bandmates Mike Campbell and Benmont Tench and producer Ryan Ulyate. “If you knew nothing about the guy, it would still be a really good set of songs you could get into and love," Ulyate said. "It’s designed to tell you a story.”

Campbell recently said a Wildflowers box set based on Petty's 1994 LP and live recordings from 1997 might be among the future releases, along with the possibility of deluxe editions of some of Petty’s other albums.

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