Before there was Black Sabbath, there was Earth (and, technically, before there was Earth, there was The Polka Tulk Blues Band). As Black Sabbath prepares for its farewell with Ozzy Osbourne on Saturday, the forefathers of metal have confirmed a new archival release culled from their early days, Earth: The Legendary Lost Tapes, out July 25th via Big Bear Records.

Ozzy, Tony IommiGeezer Butler, and Bill Ward first came together in 1968 as The Polka Tulk Blues Band, named after Ozzy’s mom’s favorite brand of talcum powder. In addition to the iconic Sabbath quartet, Polka Tulk included slide guitarist Jimmy Phillips and saxophonist Alan Clarke, who were eventually annexed after Iommi determined they lacked the necessary dedication to the band.

With the newly slimmed-down four-man lineup, the band renamed itself Earth. The group would ultimately change its name to Black Sabbath in 1969 after learning they were being mistaken for another English band called Earth, taking the Sabbath name from a 1963 Italian horror movie. Twenty years later, groundbreaking Olympia, WA drone metal band Earth would take up the name.

The Legendary Lost Tapes come from a 1969 session at Zella Studios in the band’s hometown of Birmingham, England. According to the band’s first manager Jim Simpson, who paid for the recording session and is releasing the album without the active involvement of any Sabbath members but also without protest, they didn’t release the recordings at the time because “their style was evolving so quickly.”

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“These recordings trace the development of Earth,” Simpson said, “from their days as a blues band through an experimental period to the very threshold of the music that propelled these four young men into the spotlight and defined Heavy Metal.”

The album includes blues standards “Blue Suede Shoes”, “Evenin'”, and “Wee Wee Baby” plus four originals: two versions of “Song For Jim” (named for Simpson), “Free Man”, “Wicked World”, and a 12-minute “Warning”. The second version of “Song For Jim” features Iommi on flute and clocks in at ten minutes while “Wicked World” and “Warning” would wind up on Sabbath’s self-titled debut the following year. The trio of electric blues standards highlights the band’s roots, while the foursome of blistering, lengthy originals portends the heavy metal sound they were on the cusp of creating.

“Now, some 57 years later, the recordings assume a greater importance,” Simpson said, “illustrating how these four young men from Birmingham, barely out of their teens, were excellent musicians and a fine band, fully deserving of all the success that was to come their way.”

Though Sabbath has made no official announcement regarding Earth: The Legendary Lost Tapes, the band seemed to endorse its release by sharing a trio of singles on its official YouTube channel. Fans can listen to “Warning”, “Wicked World”, and the version of “A Song For Jim” with Iommi on flute below.

Earth — “Warning”

Earth — “A Song For Jim (Flute Version)”

Earth — “Wicked World”

These singles come on the precipice of Ozzy Osbourne’s Back To The Beginning farewell concert. The Ozzman will say goodbye on Saturday with a sold-out, day-long show at Birmingham’s Villa Park featuring MetallicaSlayer, Tool, PanteraAlice in ChainsMastodonAnthrax, and many more, plus a slew of special guests like Billy Corgan, SlashDuff McKaganK.K. DowningSammy HagarFred Durst, and others all under the guidance of musical director Tom Morello. This will mark the first performance by the original lineup of Osbourne, Iommi, Butler, and Ward in 20 years.

Fans from around the world can tune in to the pay-per-view livestream here, beginning at 10 a.m. ET. If you’re lucky enough to be in Birmingham this weekend, Big Bear is hosting a series of 18 free concerts around the city, fittingly dubbed The Visit of Oz. Find a full schedule on the label’s website.