from allmusic: Commonly dismissed as a disappointment upon its initial release, the soundtrack to Led Zeppelin's concert movie The Song Remains the Same is one of those '70s records that has aged better than its reputation – it's the kind of thing that's more valuable as the band recedes into history than it was at the time, as it documents its time so thoroughly. Of course, that time would be the mid-'70s, when the band was golden gods, selling out stadiums across America and indulging their wildest desires both on and off stage. It was the kind of excess that creates either myth or madness, and this 1976 live album – comprised of highlights from their three shows at Madison Square Garden during July 1973 – has its fair share of both, as Zeppelin sounds both magnificent and murky as they blow up songs from their first five albums to a ridiculously grand scale

from allmusic: Encompassing heavy metal, folk, pure rock & roll, and blues, Led Zeppelin's untitled fourth album is a monolithic record, defining not only Led Zeppelin but the sound and style of '70s hard rock. Expanding on the breakthroughs of III, Zeppelin fuse their majestic hard rock with a mystical, rural English folk that gives the record an epic scope. Even at its most basic – the muscular, traditionalist "Rock and Roll" – the album has a grand sense of drama, which is only deepened by Robert Plant's burgeoning obsession with mythology, religion, and the occult. Plant's mysticism comes to a head on the eerie folk ballad "The Battle of Evermore," a mandolin-driven song with haunting vocals from Sandy Denny, and on the epic "Stairway to Heaven." Of all of Zeppelin's songs, "Stairway to Heaven" is the most famous, and not unjustly. Building from a simple fingerpicked acoustic guitar to a storming torrent of guitar riffs and solos, it encapsulates the entire album in one song. Which, of course, isn't discounting the rest of the album. "Going to California" is the group's best folk song, and the rockers are endlessly inventive, whether it's the complex, multi-layered "Black Dog," the pounding hippie satire "Misty Mountain Hop," or the funky riffs of "Four Sticks." But the closer, "When the Levee Breaks," is the one song truly equal to "Stairway," helping give IV the feeling of an epic. An apocalyptic slice of urban blues, "When the Levee Breaks" is as forceful and frightening as Zeppelin ever got, and its seismic rhythms and layered dynamics illustrate why none of their imitators could ever equal them.

from allmusic: Originally unveiled in December 1975, TNT was the second AC/DC album released in their native Australia, but is often overlooked outside the Land Down Under because its best tracks were later combined with those from the band's first domestic album, High Voltage, for reissue as their international debut from 1976 — also entitled High Voltage. Confused? That's actually quite understandable, since the songs culled from TNT also formed the backbone of that international release, including the entire, flawless first album side, made up of such all-time classics as "It's a Long Way to the Top," "Rock 'n' Roll Singer," "The Jack," and "Live Wire." TNT's B-side was nearly as formidable: boasting both of those Australian album title tracks — the proto-punk crunch of "T.N.T." and the suitably electrifying "High Voltage" — as well as a much-needed remake of the group's very first single, "Can I Sit Next to You Girl," recorded two years earlier with original singer Dave Evans. All three also made it into the international edition of High Voltage, and as for the two tracks that did not: one was concert favorite, "Rocker," which would be duly unearthed for the Dirty Deeds Done Dirt Cheap LP, a short time later; and the other was a reverential but not exactly life-altering cover of Chuck Berry's "School Days," which eventually surfaced on the Bonfire box set. In other words, TNT, though largely lost to ancient history, was a stellar album in its own right, and especially crucial in that it marked AC/DC's definitive break with their now seemingly heretical glam rock inclinations, in order to embrace the blue collar hard rock hat would forever after be their trademark.

from allmusic: Countdown to Ecstasy wasn't half the hit that Can't Buy a Thrill was, and Steely Dan responded by trimming the lengthy instrumental jams that were scattered across Countdown and concentrating on concise songs for Pretzel Logic. While the shorter songs usually indicate a tendency toward pop conventions, that's not the case with Pretzel Logic. Instead of relying on easy hooks, Walter Becker and Donald Fagen assembled their most complex and cynical set of songs to date. Dense with harmonics, countermelodies, and bop phrasing, Pretzel Logic is vibrant with unpredictable musical juxtapositions and snide, but very funny, wordplay. Listen to how the album's hit single, "Rikki Don't Lose That Number," opens with a syncopated piano line that evolves into a graceful pop melody, or how the title track winds from a blues to a jazzy chorus — Becker and Fagen's craft has become seamless while remaining idiosyncratic and thrillingly accessible. Since the songs are now paramount, it makes sense that Pretzel Logic is less of a band-oriented album than Countdown to Ecstasy, yet it is the richest album in their catalog, one where the backhanded Dylan tribute "Barrytown" can sit comfortably next to the gorgeous "Any Major Dude Will Tell You." Steely Dan made more accomplished albums than Pretzel Logic, but they never made a better one.

From Allmusic: Led Zeppelin's fourth album, Black Sabbath's Paranoid, and Deep Purple's Machine Head have stood the test of time as the Holy Trinity of English hard rock and heavy metal, serving as the fundamental blueprints followed by virtually every heavy rock & roll band since the early '70s. And, though it is probably the least celebrated of the three, Machine Head contains the "mother of all guitar riffs" — and one of the first learned by every beginning guitarist — in "Smoke on the Water." Inspired by real-life events in Montreux, Switzerland, where Deep Purple were recording the album when the Grand Hotel was burned to the ground during a Frank Zappa concert, neither the song, nor its timeless riff, should need any further description. However, Machine Head was anything but a one-trick pony, introducing the bona fide classic opener "Highway Star," which epitomized all of Deep Purple's intensity and versatility while featuring perhaps the greatest soloing duel ever between guitarist Ritchie Blackmore and organist Jon Lord. Also in top form was singer Ian Gillan, who crooned and exploded with amazing power and range throughout to establish himself once and for all as one of the finest voices of his generation, bar none. Yes, the plodding shuffle of "Maybe I'm a Leo" shows some signs of age, but punchy singles "Pictures of Home" and "Never Before" remain as vital as ever, displaying Purple at their melodic best. And finally, the spectacular "Space Truckin'" drove Machine Head home with yet another tremendous Blackmore riff, providing a fitting conclusion to one of the essential hard rock albums of all time.

from allmusic: Years of constant touring, alcoholism, and drug abuse finally began to affect Black Sabbath around the time of their sixth release, 1975's Sabotage. While it's not a bad album (in fact, it's one of their most underrated), you can sense that the magical chemistry that made such albums as Paranoid and Vol. 4 so special was beginning to disintegrate. But guitarist Tony Iommi again comes equipped with an arsenal of sturdy, ultra-heavy riffs, as evidenced by the raucous album opener, "Hole in the Sky," as well as the drug-induced anthem "Symptom of the Universe" – both tracks coming as close to garage rock as Sabbath ever got. But the album's biggest surprise is the melodic, synth-laced "Am I Going Insane (Radio)," which is more akin to '70s power pop than to the band's patented doom metal (although the lyrics are what you'd expect – detailing a person's downward spiral into dementia). Although often overlooked, Sabotage remains an interesting and challenging release.

from allmusic: Black Sabbath, Vol. 4 is just a cut below its two indisputably classic predecessors, as it begins to run out of steam — and memorable riffs — toward the end. However, it finds Sabbath beginning to experiment successfully with their trademark sound on tracks like the ambitious, psychedelic-tinged, multi-part "Wheels of Confusion," the concise, textured "Tomorrow's Dream," and the orchestrated piano ballad "Changes" (even if the latter's lyrics cross the line into triteness). But the classic Sabbath sound is still very much in evidence; the crushing "Supernaut" is one of the heaviest tracks the band ever recorded.

from allmusic: Black Sabbath's debut album is given over to lengthy songs and suite-like pieces where individual songs blur together and riffs pound away one after another, frequently under extended jams. There isn't much variety in tempo, mood, or the band's simple, blues-derived musical vocabulary, but that's not the point; Sabbath's slowed-down, murky guitar rock bludgeons the listener in an almost hallucinatory fashion, reveling in its own dazed, druggy state of consciousness. Songs like the apocalyptic title track, "N.I.B.," and "The Wizard" make their obsessions with evil and black magic seem like more than just stereotypical heavy metal posturing because of the dim, suffocating musical atmosphere the band frames them in. This blueprint would be refined and occasionally elaborated upon over the band's next few albums, but there are plenty of metal classics already here.

from allmusic:
Paranoid was not only Black Sabbath's most popular record (it was a number one smash in the U.K., and "Paranoid" and "Iron Man" both scraped the U.S. charts despite virtually nonexistent radio play), it also stands as one of the greatest and most influential heavy metal albums of all time. Paranoid refined Black Sabbath's signature sound — crushingly loud, minor-key dirges loosely based on heavy blues-rock — and applied it to a newly consistent set of songs with utterly memorable riffs, most of which now rank as all-time metal classics. Where the extended, multi-sectioned songs on the debut sometimes felt like aimless jams, their counterparts on Paranoid have been given focus and direction, lending an epic drama to now-standards like "War Pigs" and "Iron Man" (which sports one of the most immediately identifiable riffs in metal history). The subject matter is unrelentingly, obsessively dark, covering both supernatural/sci-fi horrors and the real-life traumas of death, war, nuclear annihilation, mental illness, drug hallucinations, and narcotic abuse. Yet Sabbath makes it totally convincing, thanks to the crawling, muddled bleakness and bad-trip depression evoked so frighteningly well by their music. Even the qualities that made critics deplore the album (and the group) for years increase the overall effect — the technical simplicity of Ozzy Osbourne's vocals and Tony Iommi's lead guitar vocabulary; the spots when the lyrics sink into melodrama or awkwardness; the lack of subtlety and the infrequent dynamic contrast. Everything adds up to more than the sum of its parts, as though the anxieties behind the music simply demanded that the band achieve catharsis by steamrolling everything in its path, including its own limitations. Monolithic and primally powerful, Paranoid defined the sound and style of heavy metal more than any other record in rock history.

from allmusic:
With Paranoid, Black Sabbath perfected the formula for their lumbering heavy metal. On its follow-up, Master of Reality, the group merely repeated the formula, setting the stage for a career of recycling the same sounds and riffs. But on Master of Reality Sabbath still were fresh and had a seemingly endless supply of crushingly heavy riffs to bludgeon their audiences into sweet, willing oblivion. If the album is a showcase for anyone, it is Tony Iommi, who keeps the album afloat with a series of slow, loud riffs, the best of which — "Sweet Leaf" and "Children of the Grave" among them — rank among his finest playing. Taken in tandem with the more consistent Paranoid, Master of Reality forms the core of Sabbath's canon. There are a few stray necessary tracks scattered throughout the group's other early-'70s albums, but Master of Reality is the last time they delivered a consistent album and its influence can be heard throughout the generations of heavy metal bands that followed.

from all music:
After staking out new territory with the underrated South of Heaven, Slayer brought back some of the pounding speed of Reign in Blood for their third major-label album, Seasons in the Abyss. Essentially, Seasons fuses its two predecessors, periodically kicking up the mid-tempo grooves of South of Heaven with manic bursts of aggression. "War Ensemble" and the title track each represented opposite sides of the coin, and they both earned Slayer their heaviest MTV airplay to date. In fact, Seasons in the Abyss is probably their most accessible album, displaying the full range of their abilities all in one place, with sharp, clean production. Since the band is refining rather than progressing or experimenting, Seasons doesn't have quite the freshness of its predecessors, but aside from that drawback, it's strong almost all the way from top to bottom (with perhaps one or two exceptions). Lyrically, the band rarely turns to demonic visions of the afterlife anymore, preferring instead to find tangible horror in real life – war, murder, human weakness. There's even full-fledged social criticism, which should convince any doubters that Slayer aren't trying to promote the subjects they sing about. Like Metallica's Master of Puppets or Megadeth's Peace Sells…but Who's Buying, Seasons in the Abyss paints Reagan-era America as a cesspool of corruption and cruelty, and the music is as devilishly effective as ever.