Metallica on Tuesday (June 22) shared an audio preview of their previously unreleased July 12, 1990, demo of "Enter Sandman."

The issue of the basement recording represents an unprecedented lifting of the veil on the inner workings of the band's hit 1991 The Black Album single that would go on to become their signature song.

The demo emerged as part of the many audio gems now being uncovered for Metallica's upcoming comprehensive reissue of The Black Album, out Sept. 10. The rough recording appears on the deluxe box set edition's second disc, called Riffs, Demos, Rough Mixes and Easy Listening Music, included alongside the remastered album and a collection of live tracks.

But that's not all Metallica's planning to celebrate The Black Album. A separate tribute album called The Metallica Blacklist also arrives on Sept. 10. It contains Metallica songs re-recorded by various artists, such as Ghost and Weezer each trying their hand at "Enter Sandman." Ahead of its release, listeners have been treated to Miley Cyrus' version of "Nothing Else Matters" and Colombian singer Juanes' take on "Sandman."

But those cover versions and the Black Album reissue might not have ever been realized if Metallica's Kirk Hammett hadn't included his "Sandman" guitar riff as an idea on a "Riff Tape" he presented to the band over 30 years ago. Metallica's James Hetfield and Lars Ulrich tracked the vocal-less 1990 demo available below.

"This unreleased demo was recorded by James and Lars in Lars' basement on July 12, 1990," the band says.

"It's finally here!" an announcement for the reissue exclaims. "Metallica's eponymous album, better known as The Black Album, is remastered and will be available everywhere on September 10th. [It is] is one of the most commercially successful and critically acclaimed records of all time, with global sales of over 35 million."

Metallica, "Enter Sandman" Demo

2021's Best Rock + Metal Albums (So Far)

Loudwire's picks for the best rock + metal albums of 2021 so far

More From 92.9 WBUF