Does a list of the rock’s all-time great records exist that doesn’t contain A Night at the Opera? From Rolling Stone’s “500 Greatest Albums of All Time” to the 2005 tome 1001 Albums You Must Hear Before You Die, the highly influential album is ubiquitous. Forty years after its release, Queen’s masterwork — anchored by “Bohemian Rhapsody,” one of the most audacious songs in pop history — has lost none of its luster. Freddie Mercury’s flamboyantly acrobatic vocals, Brian May’s ingenious guitar layering and the stunningly agile rhythms of bassist John Deacon and drummer Roger Taylor continue to dazzle like the Queen’s Crown Jewels. Yet A Night at the Opera is far more than the sum of its spectacular parts. In terms of pure sensation, it is an exquisite tour de force, one that collapses the whole of pop music history — rock, pop, jazz, vaudeville, music hall, camp, psychedelia — in on itself. Every last second is geared toward not just sucking listeners into its unique world, but overwhelming them with its endless array of delights.

Reportedly the most expensive record ever produced when it was released in 1975, A Night at the Opera was the first album to successfully integrate the power and bombast of hard rock/heavy metal (Led Zeppelin, Deep Purple, The Who) and the craftsmanship and sophistication of art pop (The Beatles, Bee Gees, The Kinks). Outside of Roy Wood’s The Move, who came awfully close with the 1970 cult classic Shazam, no band had dared cross the two streams. Before Queen came along hard rock/heavy metal and art pop appeared to be like oil and water. The former is single-minded its devotion to brute force and sweaty grooves, while the latter embraces studio wizardry, pastiche and compositional finesse.

Yet the quartet proved to possess all these traits (and then some). Not only does A Night at the Opera effortlessly swing between the two poles (the macho riff-rager “Sweet Lady” giving way to dainty ditty “Seaside Rendezvous” is pure magic), but the record also contains numerous examples of unbridled fusion. With its Beatles-esque harmonies and May’s ax slashing here, there and everywhere, opener “Death on Two Legs (Dedicated To…)” may well be the first art-metal song.

The sheer number of artists and bands that Queen’s metal-meets-pop concept inspired is staggering. Faith No More, My Chemical Romance, Jellyfish, Andrew W.K., Muse — the list goes on. Even avant-pop guitarist Marnie Stern sounds as though she spent a few years studying May’s singular guitar style.

A Night at the Opera is advanced, elaborate and bold. But beneath all the highfalutin studio processes and songwriting brilliance is something wonderfully simple, and it’s the record’s secret weapon: humor. The ’70s were the height of rock pretense, and A Night at the Opera is one of the decade’s defining moments. It was pretense delivered with a wink. It’s a fun record, silly even. Queen certainly displayed some serious prog chops through the years, but they never were serious and stone-faced like Yes or Genesis. A Night at the Opera unfolds like a surreal cartoon: technicolor splendor riddled with goofy gags, cheeky jokes and studio-generated absurdities. After all, the record is named after a Marx Brothers flick.

The six-part “Bohemian Rhapsody,” of course, drives this point home with masterful flair. It opens as a cryptically sinister piano ballad — “Mama, just killed a man/Put a gun against his head” — before exploding into a kitschy parody of classical music. It’s ridiculous and bizarre, yet utterly passionate. You can’t help but get swept away by the music’s gaudy beauty.

Maybe an even better example is the eight-minute “The Prophet’s Song,” its middle section in particular. For well over two minutes an a capella Mercury builds a chorus of his own voice (the record’s use of multi-tracking is some of rock’s best) into some kind of garish, postmodern Gregorian chant. There’s something about it that’s just so unabashedly freaky and ludicrous. Why would anybody carry on like that? But that was one of the endearing charms of the always eccentric Freddie Mercury. On A Night at the Opera , he and Queen let their freak flags fly and have a blast waving them in people’s faces. Happy 40th Anniversary to one rock’s great masterpieces!