Rush's fifth album, 1977's A Farewell to Kings, just might have been the most crucial release of their young career.

If you were to pinpoint the year that progressive rock died, 1977 is your best bet. Punk and disco were king, and critics had more or less written off progressive rock midway through the decade. But for Canada's head-honchos of prog, the year wasn't about snot-nosed three-chord anarchy or spandex pants.

Among the usual pile of critical slaying, Robert Christgau's now-infamous review labeled the trio "the most obnoxious band currently making a killing on the zonked teen circuit." To his credit, Rush were, at this point in their evolution, very much still a "love them or hate them" proposition, with the chief breaking point being bassist Geddy Lee's piercing, speaker-blowing voice, which reached some of its most shocking heights on A Farewell to Kings' closing epic, "Cygnus X-1 Book I: The Voyage," a 10-minute behemoth with outlandishly cartoonish vocals.

"Cygnus," the first installment of a two-part suite that concludes on the band's subsequent album, 1978's Hemispheres, finds drummer Neil Peart at his most lyrically pretentious. Peart's over-the-top storyline (space age explorer sucked into black hole, witnesses a metaphysical war between Greek Gods Apollo and Dionysus) ranks among the most bloated in the prog-rock canon, somewhat deserving of its critical mockery.

Musically, the track rambles a tad, though it's punched up by Alex Lifeson's intricate, funky guitar strut during the early stretches. Overall, the first half pales in comparison to the more fluid, exploratory second round found on Hemispheres. From a lyrical standpoint, compared with Peart's more subtle, nuanced writing from the band's '80s commercial peak, a track like "Cygnus" feels more regressive than progressive.

As demonstrated by "Cygnus" (and much of the material from Hemispheres), Rush weren't quite out of their sci-fi phase just yet. But A Farewell to Kings finds the band at an interesting bridge between their early '70s hard-rock excess and the more focused attack they harnessed early in the following decade. Rush were the last of the major prog bands to embrace the synthesizer.

Listen to Rush Perform 'Closer to the Heart'

Released in September 1977, A Farewell to Kings found Rush taking their first baby steps toward a very fruitful sonic relationship with the instrument, utilizing synths for texture and melodic counterpoint on the brief, atmospheric ballad "Madrigal" and the intro to the relentless, Kublah Khan-centric masterwork "Xanadu." But they still made plenty of space to flash their technical chops.

Lee's bass lines are both punchy and forceful, anchoring even the spaciest moments with quick-fingered melodic heft. Lifeson cranks out his usual quota of ringing riffs and psychedelic solos (the best of which being his wah-wah explosion on "Cinderella Man," a rare track featuring lyrics written by Lee), in addition to tasteful classical guitar work – his intro to the opening title track is among progressive rock's most iconic moments of reflective acoustic bliss.

And the mind-melting Peart continued to expand the vocabulary of rock drumming. He pulled out all the bells and whistles – literally – on A Farewell to Kings ("Xanadu" alone has intricate wind chimes, temple blocks, bell trees, glockenspiels and tubular bells).

But Rush also demonstrated some forward-thinking restraint on their fifth album, particularly on "Closer to the Heart," an exceptional ballad-turned-rocker that earned the band their first legitimate "hit," peaking on the U.K. singles chart at No. 36 in February of the following year. With Peart's reflective lyrics and the band's sensitive touch, it became an instant live staple, also helping make A Farewell to Kings their first gold album in the U.S.

"There was a feeling that the song had changed a bit," Lifeson told Guitar for the Practicing Musician in 1991. "It opens up into a bit more of a ham towards the end. It probably translates better live, visually, than it does on the record. But there is an energy to it, and it's a very positive song. It's been connected with the band for over 13 years."

Lifeson has a point. Certain moments on "Closer to the Heart," like other moments throughout the album, haven't aged gracefully. But even the most mediocre moments here have their importance. A Farewell to Kings remains a versatile, technically dazzling, and mostly unpretentious experience.

This album proved these three prog-rock amigos were invested in the genre for the long haul, even if most of their peers had already abandoned ship.

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