Kenny Chesney thought he knew how his new album, Silver Sands Marina, was going to end. Then he heard a song that changed everything.

• Silver Sands Marina is Chesney's 21st studio album.
• It's due for release on Sept. 25.
• The project has 11 tracks and includes collaborations with Megan Moroney, Colbie Caillat and Lily Meola.

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The final track on the album is "Shot Glass," a song co-written by Chesney's old friend Brett James. James died in a plane crash last September. In fact, Silver Sands Marina will come out just seven days after the one-year anniversary of his death.

Remembering a late, seminal country songwriter is part of why Chesney included the song. But "Shot Glass" is special beyond that, too: It sums up the singer's relationship with his friend, and encapsulates the spirit behind much of this album.

During a conversation with Holly Gleason streamed on TalkShopLive, Chesney picked out one lyric from the song that spoke to him.

"At the end of the song, it says, 'Tell me, how did all that fit into a shot glass?'" he relates. "Now, to sing that song, you have to have lived a little bit. You have to have a little bit of perspective."

That sentiment spoke to the rest of the record, and all the emotions Chesney covers on those songs. It also spoke to the singer's friendship with James.

"Then I think about my friend Brett, and his life, and how much fun we had together and all the journeys we went on. All the sunsets and boat trips and songs written during that period," Chesney remembers. "How did all that fit into a shot glass?"

"I knew exactly how I wanted this album to end," he adds, "And then I heard 'Shot Glass.'"

Brett James was killed in a small-engine plane crash in North Carolina on Sept. 18. His wife and step-daughter also died in the crash.

Over the course of his songwriting career, James wrote for big stars like Chesney, Dierks Bentley, Rascal Flatts and Martina McBride. He's also credited for helping kickstart Carrie Underwood's career, penning hits like "Jesus Take the Wheel" as well as "Church Bells," "Love Wins," "Cowboy Casanova," "The Champion" and her Miranda Lambert duet "Somethin' Bad."

Read More: Kenny Chesney In Shock After Brett James' Death: "I Didn't Want to Believe It"

Chesney, like several other stars, shared an emotional tribute to James after his death.

"Brett and I shared a unique bond. A brotherhood. A kinship," he said in that post.

"Thank you for being a lifer, for being a shirtless, sunburned troubadour, for your friendship, your songs and all the laughs," he added in a message addressed to James.