Walter Parazaider, a co-founding member of the rock band Chicago, has died at the age of 81 following a battle with Alzheimer’s disease.

His daughter confirmed the news in a Facebook post on Wednesday morning.

“My father, my hero, is gone. He went peacefully about 20 minutes ago,” she wrote. “There’s no more pain. No more struggle … This was the worst six years. The hardest season of my life. And I’m so grateful that my dad is not suffering anymore. I love you poppy, my Pal.”

Parazaider was a co-founder of the group best known for 1970s and 80s soft rock classics like If You Leave Me Now and Hard to Say I’m Sorry. He played reed instruments and saxophone with the band from its inception in the late 60s to his retirement in 2018.

“He had put up a good fight with Alzheimer’s and unfortunately it ended tonight,” his wife JacLynn told TMZ. “We are going to miss him for sure ... We were married for 59 years and we had 59 wonderful years.”

Born in the small town of Maywood, Illinois, Parazaider was inspired by the Beatles’ work on Revolver to start a rock band with a horn section, and helped found Chicago (initially called the Big Thing) in 1967 with Peter Cetera, Terry Kath, Robert Lamm, Lee Loughnane, James Pankow and Danny Seraphine.

“A Rock & Roll band with horns was Walt’s idea,” the band said in an Instagram statement. “He put the band together and they rehearsed in the basement of his mother’s home. He is also the one who did the hard work to book shows for the young, unknown band, performing top 40 covers at local bars in and around Chicago.”

As founding member Lee Loughnane put it in an interview with The Guardian, “We just got together and did a rehearsal at Walt’s basement and we never stopped playing together again.”

“It sounded great and we enjoyed it. We liked what it sounded like and every gig that we had from that time on – we started booking club dates – and we just learned enough songs to get through the night because we were playing like six hours a night: 45 on, 15 off.”

Parazaider played the well-known flute solo in the 1970 Chicago single Colour My World, as well as the recognizable saxophone on 1973’s top five hit Just You ‘n’ Me.

In 1976, Chicago reached number one in the US and UK with the soft rock balled If You Leave Me Now, written and sung by bass player Peter Cetera. The song was certified platinum and has been extensively used in films such as Shaun of the Dead, The Secret Agent as well as a fan-favorite episode of Sex and the City.

Chicago continued to have hits into the 80s with top 10 singles including Will You Still Love Me?, Look Away and What Kind of Man Would I Be? The band was inducted in the Rock & Roll Hall of Fame in April 2016.

In their Instagram statement, Chicago wrote: “We are forever grateful for his contributions. Perhaps his greatest gift was bringing people together. This amazing music may have never been heard had it not been for Walt’s vision.”