Beach Boys Al Jardine and Mike Love were in good spirits when asked about Disney’s upcoming documentary on the pop music pioneers at a press conference earlier this month.

“It wasn’t a problem signing up for it,” said Love. “Its’ a phenomenal at this stage of our career to see all the hard work and forensics going into this documentary.

“When I look at the film, I feel some sadness because Dennis is gone, Carl is gone, Brian’s had his rough times. But there’s an awful lot of appreciation for the work we did together and the music that united us, even in spite of individual differences."

Directing the doc was “a dream come true” for lifelong Beach Boys fans Frank Marshall and Thom Zimny, who’s respective CV’s include films on the Bee Gees, Johnny Cash and Elvis. In order to bring the band’s story to life, the pair sieved through a mountain of never-before-seen footage and photos.

“One of the things I love about making docs the treasure hunt, you never know when you’re going to find a gold nugget that can to take you in another direction,” said Marshall. “It's a journey of discovery and it’s thrilling when you find something that you realise no one has seen before.

“For me, it was the joy of being a kid that I saw in all of the different band members. They grew up like I grew up, having fun and goofing around.

“I was in a band when I was younger too and I think the world is lucky that I didn’t go the same way they did. But it was fascinating to understand how their band worked and mine didn’t. Talent might have been the key.”

“The music is timeless, and the body of work is so big,” added Zimny. “There’s so many things to dive into. I hope this documentary reflects the family, but also the individual members, what they bring musically and the positive energy that the tracks brought to me as a fan.”

LOS ANGELES - CIRCA 1964: Rock and roll band "The Beach Boys" pose for a portrait with 2 Honda Mo-peds in circa 1964 in Los Angeles, California. (L-R) Al Jardine, Mike Love, Dennis Wilson, Brian Wilson, Carl Wilson. (Photo by Michael Ochs Archives/Getty Images)

The feature prompted a Beach Boys reunion, with one scene depicting the remaining members reuniting at the storied Paradise Cove in Malibu, the same location where the cover to 1962’s Surfin’ Safari was shot.

“Frank [Marshall] gave me Jimmy Buffett’s guitar and asked me to play some songs,” said Jardine.

“It was my idea to get the guys together, it was just like when we started. We did ‘Surfin’ Safari’. We did ‘Fun, Fun, Fun’. Paradise Cove is where it all started and I just enjoyed the heck out of it.”

“It was a total joyous reunion in a sense because there’s been separations and stuff like that,” said Love. “When we get together, we unite through harmony and positivity. There’s a basis of love and respect for each other’s individual abilities.”

These harmonies are front and centre in the film, which dedicates plenty of runtime to the band’s work in the studio.

“Whenever we started a song, it was already in Brian’s head,” said Jardine of their creative process. “Brian would put his right hand on the piano, and each one of us was a note. The trick was you had to remember your part. If you didn’t, it screwed it all up and we had to start over.”

1964: Al Jardine, Brian Wilson, Mike Love, Carl Wilson and Dennis Wilson of the rock and roll band "The Beach Boys" sing around a piano . (Photo by Michael Ochs Archives/Getty Images)

While Brian Wilson is often rightly lauded for his genius, The Beach Boys shines a light on each individual band member and their underrated contributions to the collective.

“It’s the sum of all the parts,” said Marshall. ”You take one out, and you don’t have The Beach Boys. Somehow those guys were able to blend this sound and make it unique.”

“We were obsessed by not only the harmonies and the notes, but the blend,” added Love. “Anybody can sing a note, but can four people blend together? That was our obsession.”

This obsession culminated in a plethora of unforgettable hits, not least the Beach Boys’ 1966 Opus Pet Sounds, which tops many musicologists’ ‘Greatest Albums of All Time’ lists.

“I just think the beauty of Pet Sounds is that it challenged the idea of what the pop song can be,” said Zimny. “It created a new sonic landscape. Music changed at that point.”

LOS ANGELES - 1966: Singer and mastermind Brian Wilson of the rock and roll band "The Beach Boys" directs from the control room while recording the album "Pet Sounds" in 1966 in Los Angeles, California. (Photo by Michael Ochs Archives/Getty Images)

While the music might have changed, the band's ability to draw in new audiences hasn't. The Beach Boys documentary very much acts as a testament to the group’s longevity. What, in their eyes, has made them stand the test of time?

“We used to say we appealed to the eight to eighty group. Well, know we’re eighty”, quipped Jardine.

“It’s universal,” he continued.  “People are learning via social media too. When I was in high school, I couldn’t even imagine seeing or hearing from the bands that had number one hits in the ‘50s. Now you can learn about the catalogue so quickly."

“The music is immortal,” added Love.  “We aren’t, but the music is.

“In Sheffield, a psychologist studied which songs made people feel the best and ‘Good Vibrations’ came in at number one.

"I think because of the negativity in the world, our music has always been a release and celebration of life, we didn’t choose to sing about negative things, although there were plenty of negative things going in the ‘60s, just like there are now.”

• The Beach Boys will be available to stream on Disney + from May 24. Watch the trailer below.