Katastro Shares New Music Video for 'Our Favorite Song,' Featuring Vocals from Late Lead Singer Andy Chaves (Exclusive)

Andy Chaves never liked to write nice songs about nice girls. But on a March day in 2022, the lead singer of the Arizona-based alternative band Katastro seemed as if he wanted to do something completely different.

"A lot of our songs are about Andy's breakups and rough situations with women in his life, but he was just in a good mood that day," Katastro drummer Andrew Stravers, 34, remembers during a recent interview with PEOPLE from the Arizona studio where the band gathered that fateful day two years ago. "He was like, 'You know what? I want to write something sweet and a little more genuine about a girl.’ I was like, 'That's nice. You should do that.'"

And so, he did. But never could anyone imagine that Chaves wouldn't be here in this moment, singing the song that took him so long to write.

Three months later, in May 2022, Chaves was killed in a car accident. He was just 32 years old.

"The night of Andy's funeral, we all went back to his family's house," Stravers says quietly. "There were probably 40 family members at his parents' house, and they asked, ‘Do you guys have any demos?’ And I showed them this song."

At the time, the song that held Chaves’ precious vocals was only known by the title "Dancing."

"I played it for them and the whole family went from crying and being sad to standing up and dancing," Stravers remembers. "At that point, it was like a minute and a half demo. I think we played it a total of 15 times. And so, from that moment on, it was a big thing that we wanted to finish it for not only the album, but for his family too."

Of course, the act of finishing the song came with an enormous amount of pain, as it meant that the remaining members of Katastro — Stravers, bassist Ryan Weddle and guitarist Tanner Riccio - needed to dig back into the song that their friend never finished.

"Finding demos on our hard drives after the fact showcased, in my opinion, how talented Andy was and just how gifted he was," says Stravers. "We actually turned ['Dancing'] into a Katastro song where Tanner took out his guitar and did his thing, and Ryan did his thing with the bass, and it transformed into one of our favorite songs on the album."

And that's why they called the new single — the music video for which PEOPLE is exclusively premiering — “Our Favorite Song."

"We kind of just handed the reins to [video director Dylan Toon] and he told us what he thought," Riccio, 35, tells PEOPLE of the surprisingly upbeat music video. "With [Toon] being the professional and knowing what to do, we just trusted that, and it came together really well, even better than we thought."

So too has their seventh full-length album, which will now forever serve as the home to "Our Favorite Song."

"The entire album was made from vocal takes that we had from [Chaves] from completely unfinished songs and super rough demos," Stravers says of the forthcoming album Until the End of Time, which is set for release on Oct. 4 and includes the talents of fellow artists such as Dirty Heads, Iration and Rome Ramirez. "Finishing the songs with his vocals was a huge part of us getting through the past couple years and getting over the situation of losing our best friend."

"We didn't even know if we could put an album together initially," Riccio adds. "It took us a while to have the confidence that we could put out a good record that sounds like it's not pieced together. I think we're still taking it in and still not realizing what we've done."

Because as much as the loyal fanbase of the Katastro needed this album to come to fruition, so did the members of the band.

"Over the past two years, [we all] needed to listen to his voice and work on these songs so that we could get through it," Stravers says. "And if it doesn't do anything and only 10 people stream it after the album comes out, it already served a massive purpose for helping us get through Andy's death. That's the way I feel about it."

Each member of Katastro also feels that this is the last album they will ever put out as a band.

"It's bittersweet knowing that we're not working on something together that includes him after this process," says Riccio. "But again, it's very healing to finish it and get it out there for everybody to enjoy."

And they believe Chaves would have enjoyed it too.

"He better know right now how hard this s--- was," says Riccio. "He better know."