Among the truly great heavy metal albums, Alice in Chains' masterpieceis easily a cut above the rest.

Released in September, 1992, Dirt took the Seattle band to No. 6 on the U.S. Billboard chart, no small feat for band that got little airplay and a record with drug addiction, depression and anger as central themes.

But, aside from the lyrics and amazing songs, what makes Dirt such a great record is how good it sounds.

Produced by Dave Jerden, who also worked with AIC on their debut Facelift album, Dirt has a doomy, heavy sound that announced the band as one of the heavy hitters in rock at the time.

And central to that amazing sound is how guitarist and principal music writer Jerry Cantrell got those super thick and heavy guitar tones.

Turns out Cantrell actually recorded each riff through high, mid and low frequency amps to get three different tones. Then those tracks were double and triple tracked to fatten up the sound. Jerden and engineer Bryan Carlstrom built a customized splitter box that split the guitar into the three amps and cut down on the hissing and buzzing created from such a process.

You can really hear the thickness in songs like "Them Bones" and "Rooster".

In an interview with Music Radar, Jerden credits Metallica drummer Lars Ulrich for helping him find the right drum sound at One On One Studio in LA that helped Sean Kinney sound like a monster on

"We recorded it at One On One, where Metallica did their "Black" album. Lars told me that they had this 31-inch woofer for the kick drum. I rented a PA system and put the kick drum, toms and snare through this woofer plus these huge side monitors," Jerden told Music Radar. "That went into the room sound, and it made the drums sound like artillery going off. I credit Lars with turning me on to that room."

Those who have read David de Sola's book "Alice in Chains: The Untold Story" will know that Layne Staley didn't like anyone watching him lay down the vocals. And that was the case recording Dirt. Staley would go into the booth by himself and cut vocals. He usually did them very quickly, with minimal retakes, in total privacy.

Staley's Vocal Booth Shrine

In de Sola's book, Carlstrom recalls Staley had created an inspirational shrine in the booth that included candles and a picture of the Last Supper, as well as a dead puppy in a jar.

As for how Jerden produced Staley's booming voice, he said he had two 24-track machines and used 16 tracks for Staley's vocal parts.

"I tripled-tracked him, and he sounded great. He knocked out his parts and just sang great. I made this effect using delays on Layne’s vocals with an Eventide Harmonizer; in fact, I called the effect ‘Layne Staley.’ Reverb can darken things up, but delays keep things hard and powerful," said Jerden. "None of the mixes took long. A lot of them were done in just half an hour."

Naturally, the songs speak for themselves on Dirt: A collection of phenomenal music with nary a filler track to be found (except for the 44-second "Intro: Dream Sequence). The songs are propelled by the stunning harmonies of Staley and Cantrell's voices, particularly on "Down in a Hole", "Them Bones", and the Staley-penned "Angry Chair", which those who have gone through drug rehab say is a song about the process of being in treatment and trying to kick heroin.

As for the album art, many wrongly believe the woman on the cover is Staley's then-girlfriend, Demri Parrott. In fact it's an actress named Mariah O'Brien who is laid out in the dirt of the desert. But she does look a lot like Parrott.

Suffice it to say, Dirt is a timeless album for the ages that will be enjoyed by many more generations of music fans.

Check out the five most underrated Alice in Chains songs with Layne Staley.