Jordan, who was the older brother of actor and comedian Jonah Hill, passed away in December 2017 from a blood clot in his leg. He was just 40 years old.
Opening up about the band's new single during an appearance on Monday's (October 07) instalment on "The Ellen DeGeneres Show", Adam described "Memories" as "a heavy song", before sharing the heartbreaking inspiration behind the tune.
"I had just gone through losing my manager and best friend," he shared. "I was in diapers with this guy. And he passed away recently, and so this song came to me at a very interesting time."
"I filled in the holes with the proper words that I thought would match the experience that I had been going through. It's very heavy. I have never had a song about anything quite like this."
Before joining his bandmates to perform the emotional track, he added of Jordan: "I miss him everyday and to me this is the best way to pay tribute to him."
After holding it together through the performance, the star's pal Ellen DeGeneres comforted him with a big hug as the track came to an end.