The Beach Boys’ Pet Sounds came out 50 years ago. It still feels fresh today.

You're halfway through the album when you hear it — a heavenly harmony of instruments that features a harpsichord, organ, bass clarinet, string bass, sleigh bells, and a wonderful French horn.

This is the intro to "God Only Knows," the most well-known single from Pet Sounds, the masterpiece by the Beach Boys originally released 50 years ago, on May 16, 1966.

Pet Sounds was a major turning point. Through sheer cohesiveness in its themes, song-to-song production excellence, and innovative use of instruments, Pet Sounds set a new standard for what a record album could — and should — be. It also vaulted the Beach Boys to the forefront of popular music trends.

But it didn't arrive out of nowhere. It was a product of particular circumstances, developed amid an informal competition between two behemoth musical groups.

That it gave us "God Only Knows," one of our culture’s most beloved songs, should hint at the remarkable quality of the album as a whole. So now that it's turning 50, let's figure out why it's as good as it is.

At least in part, Pet Sounds is defined by its modernization and imaginative sound

"Nah-uh, that was too jerky," Beach Boys mastermind Brian Wilson says to French horn player Alan Robinson, interrupting a take of "God Only Knows."

"Make it more ooooh-ooh," Wilson sounds out, trying to get Robinson closer to what’s in his head. Robinson does his best to play the instrument in a way that mimics what Wilson is singing. "Let’s go. Yeah. Right," Wilson tells Robinson, and the assembled group of studio session players, who have become legends in their own right.

The Wrecking Crew, as those session players were unofficially called, had to adapt to any number of requests, some more unusual than others. Throughout the recording of Pet Sounds, Wilson relied on an unusual assortment of items to add depth to the songs he had written and mostly carried in his head.

The album features an empty plastic bottle used for a percussion sound in "Caroline, No," and Wilson used empty Coke cans in a similar manner in "Pet Sounds," the track before it. You’ll hear tricycle bells and bicycle horns in "You Still Believe in Me," and sleigh bells in "God Only Knows."

Wilson also used better-known instruments in weird ways. For the intro to "You Still Believe in Me," Tony Asher, Pet Sounds' primary lyricist, helped Wilson get the sound he wanted by plucking the strings inside Wilson's piano as Wilson held down the notes on the keyboard. "I Know There’s an Answer" uses a harmonica as a bass instrument and for a solo — unheard of at the time.

And remember that eerie sound of the electric theremin in science fiction movies of the '50s and '60s? Its haunting wails turn up near the end of "I Just Wasn’t Made for These Times."

It’s impossible to say for sure where Wilson got his ideas for instrumentation, but what motivated his endless experimentation is unmistakable: his desire to beat the Beatles.

The album was a critical step in a production race that defined the music industry in the mid-1960s

The story usually goes like this: After the arrival of the Beatles in America, they and the Beach Boys entered a production race of "mutual inspiration." George Martin, the recently passed producer for the Beatles, once described it this way:

The Beatles were going their way and Brian was going his. And they were kind of looking over their shoulders and seeing what was coming up on the outside rail. And, um, I think that was the effect of it. They wanted to experiment more. They wanted to do…rather more outrageous things.

Though neither group had a specific goal in mind, we can be sure of the result: a shift toward using the recording studio as an instrument in and of itself, whether by improving the clarity of recording or by utilizing the latest technology to wield more control over the final product.

"Not until the Beatles hit — then we really felt we had to get going," Wilson said in a 2002 episode of the TV series Art That Shook the World. However, while the Beach Boys and the Beatles took small cues from each other immediately after the British Invasion, it wasn’t until the end of 1965 that the race took off in earnest. "When I heard Rubber Soul, I said, ‘That’s it. That’s all, folks,’" Wilson recalled.

Marilyn Wilson-Rutherford, his then-wife (who was just Marilyn Wilson at the time), remembers her former husband saying, "I need to make the greatest rock 'n' roll album. I’m gonna do it." The result was Pet Sounds.

Alas, much to Wilson's dismay, the album wasn’t particularly well-received in the US, peaking at 10th place on the Billboard 200. The band's label, Capitol, also released a Beach Boys greatest hits collection not too long afterward, when it looked like Pet Sounds wasn’t doing well as the band or Capitol had hoped, further kneecapping Wilson's work.

But despite its disappointing debut, Pet Sounds was tremendously influential.

The album had a warmer reception in the UK, peaking at No. 2 on the charts. And it immediately inspired the Beatles' recording of "Here, There, and Everywhere," which would appear on their own classic, Revolver, when it was released a few months later, in August 1966.

Yet Revolver’s production — with the exception of "Tomorrow Never Knows," which features looped tapes, reversed instruments, and other creative uses of the studio — lacked in comparison to Pet Sounds. It didn’t (and doesn’t) sound as full or rich.

So when the Beatles began work on 1967's Sgt. Pepper’s Lonely Hearts Club Band, Pet Sounds was at the forefront of their minds. "Without Pet Sounds, Sgt. Pepper never would have happened. ... Pepper was an attempt to equal Pet Sounds," Sgt. Pepper producer Martin wrote in the liner notes for the Beach Boys' outtakes collection The Pet Sounds Sessions, released in 1997, a year after Pet Sounds’ 30th anniversary.

Paul McCartney himself has echoed that sentiment. "If records had a director within a band, I sort of directed Pepper," McCartney said in an interview he did in 1990. "And my influence was basically the Pet Sounds album." Sgt. Pepper marked a huge production leap over Revolver, and went on to win the Beatles a Grammy for Best Album.

That's essentially where the production race ended. While the Beatles were busy with Revolver and Sgt. Pepper, the Beach Boys' Wilson had been trying to up the ante even more with SMiLE, his intended follow-up to Pet Sounds.

SMiLE was an ambitious, high-concept undertaking; Wilson was recording everything in pieces, effectively experimenting with a physical version of digital editing about 20 years before the technology arrived. But due to the huge amount of effort involved and a breakdown in Wilson's mental health, SMiLE was not to be. The project famously collapsed and wasn't released — until decades later, when it was released officially in two different versions.

What’s remarkable, though, and what has seemingly been forgotten in the decades since, is the strong possibility that by the end of 1966, Wilson had finally managed to fight the Beatles to a near draw in terms of popularity — at least when considering the two groups' chart performance in the US and the UK.

The Beach Boys' "Wouldn’t It Be Nice" and "Sloop John B," two of the three singles from Pet Sounds, charted incredibly well in the US, and "Sloop John B" also performed well in the UK. The 1966 standalone single "Good Vibrations" proved a monumental success, and the Beatles were widely feared to be breaking up in late ’66, after Revolver.

Indeed, a 1966 reader poll conducted by the UK's NME Magazine shows how close both groups were: The Beach Boys beat the Beatles by 101 votes to earn the title of Most Popular Band, 5,373 to 5,272.

So even though Pet Sounds’ success was initially disappointing, it ultimately led the Beach Boys to the height of their popularity. And while that popularity inevitably declined over the long term, what’s helped the album maintain a fervent following is the almost universally relatable journey it leads its listeners through.

As a whole, Pet Sounds tells a relatable story about young love and heartbreak

Of the many themes and subjects Pet Sounds touches upon and tackles, the album is united by a sadness it never shies away from; at its core, Pet Sounds is about young, failed love.

"God Only Knows," like most of the songs on the album, functions differently as a standalone work than within the context of the album. By itself, the song explores a person longing for her romantic partner who has died. But in the context of the album as a whole, it feels like a pivot, signifying that point in a relationship when you suspect you’re falling out of love or can begin to imagine life without the person you’re involved with.

Pet Sounds begins with "Wouldn’t It Be Nice," perhaps the record’s "happiest" song, in which a couple yearns for the bright future they anticipate having. The rest of the first side (which ends with "Sloop John B") similarly tackles falling in love or being in love in various contexts: "You Still Believe in Me" beautifully explores the feelings one experiences after letting down a partner, and how couples overcome this struggle. "That’s Not Me" concerns someone who must figure herself out — encountering dejection (and resignation, disappointment?) — before she enters a relationship.

"Don’t Talk (Put Your Head on My Shoulder)" dives into a very relatable situation: consoling a loved one through a very depressing point in her life. "I’m Waiting for the Day" explores a relationship formed in the wake of a breakup, and "Let’s Go Away for a While," the first of Pet Sounds’ two instrumental pieces, allows listeners to relax and take stock of what they've heard so far, yet still communicates a vague feeling of sadness.

"Sloop John B" finishes out the first side. As a cover of a Caribbean folk song, it's sometimes viewed as an oddity — something that doesn’t belong on an album that's ostensibly about failed romance. But when you analyze it a little more closely, you’ll find much of its subject matter at home within Pet Sounds. The song, like the rest of the album, is rooted in sadness; in this case, it's the result of a vacation gone awry, which also serves as a metaphor for the depressing journey the album takes you on.

"God Only Knows" starts the album's second half, followed by "I Know There’s an Answer," which was originally titled "Hang On to Your Ego." Like "That’s Not Me," the song is about finding oneself, but its placement on the album conveys a sense of frustration, gloom. The singer is clearly struggling to connect with someone she knows, someone who is closed off.

Not unexpectedly, "Here Today" comes next, a breakup song about seeing your ex-partner take up with someone else — a kind of inverted "I’m Waiting for the Day." "I Just Wasn’t Made for These Times" explores feeling lost in an unfamiliar environment, not unlike the "What do I do now?" feeling we might experience when a relationship ends.

Then "Pet Sounds" offers one more chance to reflect before the album concludes. Its penultimate track and the second and final instrumental, the song is far more unsettled than "Let’s Go Away for a While," reflecting its place within the album's ongoing love story.

"Caroline, No" is Pet Sounds’ piercingly vulnerable finale. Far in the future, and thus much older, our teenage ex-partners meet once again. Expanding upon the premise of how people change as they get older, the song wonders if the love these teenagers once felt for each other could ever be reignited or felt again. But its tone implies it cannot, and mourns the loss of that first love.

The conclusion of "Caroline, No" can seem bewildering, especially to first-time listeners. The sound of an oncoming train accompanied by barking dogs might be confusing in the moment, but as the train approaches and accelerates, the barking dogs chasing after it, the metaphor becomes clear: It represents the loss of innocence after your first heartbreak.

Fans of Pet Sounds have heard this train coming and going for a long time now — both when they experience it in their own lives and every time they take the record for a spin.

Forget the surfing, girls, and cars — Pet Sounds is the Beach Boys' true legacy

It’s difficult to measure cultural awareness of a particular album. However, given the Beach Boys' legacy and the relative popularity of some of Pet Sounds' singles, it’s a pretty safe bet that, as was the case in 1966, "Wouldn’t It Be Nice," "Sloop John B," and "God Only Knows" are more widely known than the album on which they debuted.

And the consequences of SMiLE’s collapse can still be felt today. After Wilson gave up on the project, the Beach Boys pulled out of the production race, stripped Wilson of his status as band leader, and released the lo-fi Smiley Smile in September of 1967. Because they stopped innovating, they very quickly fell out of fashion.

The Beach Boys didn't stop recording good music after 1967. But great albums like Sunflower, Surf’s Up, the underrated masterpiece Holland, and the more recently released SMiLE Sessions never received the public recognition they deserved. Today, the Beach Boys' image still largely reflects the band's "cars, surfing, and girls" years.

What’s heartening to see, however, is that even though the production race between the Beach Boys and the Beatles ended nearly 50 years ago, in some ways it’s still going on. Both groups have charted among the top 10 on the Billboard 200 within the past four years — pretty good for 50-year-old bands. And it's common, on lists of the best albums of all time, to see Pet Sounds jockey with a Beatles album (like Sgt. Pepper or Abbey Road) for the top spot.

But to my mind, the Beatles never topped Pet Sounds. For all the Fab Foursome's admirable achievements, they never managed to wield an album so deftly united in subject matter, theme, production, and song-to-song quality.

If you’ve listened to Pet Sounds before, listen to it again. If you haven’t, listen to it today, and discover that the best of the Beach Boys has nothing to do with the beach — it’s in that piano introduction of "You Still Believe in Me," that beautiful chorus and wonderful French horn at the end of "God Only Knows," and that train from "Caroline, No." Acknowledge the band's true legacy in the wistful, heartbroken sadness of Pet Sounds.