Tool not only mastered alt-metal with their 1992 debut EP Opiate, they gave an immediate indication of how they would advance the genre. Over the next four albums, Tool made good on that promise both musically and lyrically.

Progressively complex arrangements on each subsequent record had fans spending hours obsessively listening, then sharing deciphered meanings on the internet. As the songs grew in scope and length, they could best be described by Joe Pesci’s character in the conspiracy film JFK: “It's a mystery wrapped in a riddle inside an enigma!”

Guitarist Adam Jones and vocalist Maynard James Keenan co-founded the band in the late '80s with drummer Danny Carey and bassist Paul D’Amour. Justin Chancellor took over for D'Amour in 1995, as Tool continued to bring in elements of prog metal, thrash, industrial, math rock, art rock and psychedelic rock.

Sonically, the band's music has always been melodic yet intricate, but a lyrical pattern developed over the course of their career. While the early material dealt with anger at the establishment, Tool eventually began to concentrate on self actualization and finding enlightenment, rather than fixating on the outer world.

Here are 10 Tool songs that best represent this complex, ever-evolving group.

10. "Opiate"

From: Opiate EP (1992)

It was so close between this and “The Grudge” from Lateralus. The title track from Tool's debut release, “Opiate” offers a strong indication of where the band will evolve on their next release. Co-opting a line attributed to Karl Marx that religion is the "opiate of the masses," Keenan lashes out against the "guidance" of organized religion and strict rules that destroy the self in order to sustain the establishment. Introducing the song at the 2017 Governors Ball, he told the crowd, “Your enemy is ignorance.” Similar themes would pop up frequently on subsequent albums.

9. "Rosetta Stoned"

From: 10,000 Days (2006)

“Rosetta Stoned” returns to the unresponsive patient on “Lost Keys (Blame Hofmann),” an earlier Tool song which referenced Albert Hofmann, the father of LSD. During a hallucinatory experience, the patient encountered aliens and reached nirvana but forgot what he discovered. Concluding with a dose of scatological humor, “Rosetta Stoned” is Keenan's warning that if you're not careful with mind-altering chemicals you’re more likely to soil yourself rather than achieve a higher consciousness.

8. "Schism"

From: Lateralus (2001)

This can be viewed as a commentary on religion splintering into squabbling tribes or an attempt to resurrect a sputtering romance. Either way, like “The Grudge,” this Grammy-winning song's lyrics handily apply to a band rekindling their friendship and creative partnership after Keenan’s work with A Perfect Circle caused a rift within Tool’s ranks. A DVD single arrived three years later with a music video directed by guitarist Adam Jones that features humanoids bearing a noticeable similarity to the engineers in the Alien prequel Prometheus.

7. "Intolerance"

From: Undertow (1993)

The song’s recurring line – "lie, cheat, and steal" – derives from the West Point Military Academy's cadet honor code. Keenan picked that up when he attended the school. The song's premise is that those who remain silent while others indoctrinate the world and commit crimes are just as bad as the criminals. Apathy is never to be tolerated. "Intolerance" shares the alt-metal fury heard on Opiate but with production that packs an unending wallop and lyrics filled with much more depth.

6. "Prison Sex"

From: Undertow (1993)

The second single from Tool's full-length debut is the first to have Jones as sole video director. The guitarist went on to helm their next five clips. On the surface, this song's title can be easily misinterpreted but "Prison Sex" actually deals with sexual abuse. Using different points of view, Tool confronts how the abused child becomes damaged and grows up to continue the negative cycle as an abusive adult. During a 1996 performance, Keenan said "this song is about recognizing, identifying, the cycle of abuse within yourself. That's the first step of the process. Realization. Identifying. The next step is to work through it."

5. "10,000 Days (Wings Pt. 2)"

From: 10,000 Days (2006)

Sad yet beautiful, "10,000 Days (Wings Pt. 2)" focuses on Keenan’s mother, who suffered a stroke that left her paralyzed and in a wheelchair until she died 27 years later – nearly 10,000 days. The song boasts a sweeping rhythmic momentum that’s reminiscent of Pink Floyd’s “One of These Days.” Lyrically, Keenan admires her faith and wants it to comfort her, even though the singer recognizes his spiritual pursuits lead him away from organized religion. After the album was released, Keenan said he regretted being so emotionally vulnerable. "I think probably the stupidest thing I could have done on 10,000 Days was put myself out there as much as I did with the tracks 'Wings for Marie (Part 1)' and '10,000 Days (Wings Part 2),'" he admitted. "I'll never make that mistake again. It just took too much out of me – too much emotionally, mentally, physically."

4. "Parabola"

From: Lateralus (2001)

"Parabol” introduces this song with a singing style similar to Qawwali, a form of Sufi Islamic devotional music. Both put forward the idea of our bodies as being a temporary vessel, and that “pain is an illusion.” Uplifted by this idea, "Parabola" becomes one of the more upbeat, celebratory moments from Tool. This second single from Lateralus continues its themes of spiritual enlightenment and the practice of Buddhism’s Noble Eightfold Path, in regards to self-discipline, self-purification and the end of suffering. The video features trip-hop music pioneer Tricky, whose body eventually transcends into a translucent being similar to the figure created by visionary artist Alex Grey for the album’s artwork.

3. "Third Eye"

From: Ænima (1996)

Like the title track of Ænima, "Third Eye" is influenced by the comedian Bill Hicks, who once said: “Watching television is like taking black spray paint to your third eye.” Hicks' "One Good Drug Story" and "The War on Drugs" are sampled at the beginning of this song. The lyrics deal with the sixth chakra of spiritual power in the human body, aka the Third Eye. The music and vocal performance reflect the attempts and frustrations of “prying open” one’s third eye. It doesn’t happen here; that higher consciousness is finally achieved on the next album, Lateralus.

2. "Lateralus"

From: Lateralus (2001)

The title track from an already-intricate album upped the art-rock approach by applying the Fibonacci Sequence, wherein each number equals the sum of the two numbers that precede it. That math formula has a relationship with Phi, the golden ratio, which describes spirals in nature. Spirals are mentioned by Keenan in the lyrics, while the time signatures of the chorus change from 9/8 to 8/8 to 7/8 to symbolize a spiral. (987 is also part of the Fibonacci Sequence.) What makes "Lateralus" a wonder is that it doesn't get swallowed up, in spite of all that complexity. Instead, the music deftly supports a lyric about perseverance towards enlightenment.

1. "Sober"

From: Undertow (1993)

The first single from Tool's debut album demonstrates the band's powerful dynamics. "Sober" also highlights Keenan's strong yet emotionally nimble voice as he handles a lyric that could be as much about hitting reset on spiritual awakening as about addiction. It's possible that Tool got this so right because "Sober" had been around since 1986. A faster, different version, then titled "Burn About Out," was part of a demo cassette by Keenan's previous band, Children of the Anachronistic Dynasty.

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