Chicago founding member Walter Parazaider has died at the age of 81.

The musician lost his six-year battle with Alzheimer's - a type of dementia that impacts memory, thinking and behaviour - at 2.10am on Wednesday morning (17.06.26) while in hospice, surrounded by his wife, JacLynn.

She added to TMZ: "He had put up a good fight with Alzheimer's, and unfortunately, it ended tonight. We are going to miss him for sure ... We were married for 59 years, and we had 59 wonderful years."

In addition to JacLynn, Walter is survived by their daughters, Laura and Felicia.

Felicia shared the pain he and his family went through since Walter's Alzheimer's diagnosis in 2021, and she is glad the rocker is now at peace.

Her heart-wrenching tribute, posted on Facebook, read: "I didn't get back in time. My father, my hero, is gone. He went peacefully about 20 minutes ago. There's no more pain. No more struggle. I physically knew I wasn't going to make it back in time.

"And I knew that it would be just my mom and him. It's how it was in the beginning. Just the two of them. And so it should've been in the end. Thank you for loving my father, even if you didn't personally know him. I know that many of you loved him.

"I'm in shock and disbelief, and yet not at all. 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. You coloured our world. God bless you, you dear soul. I love you beyond thoughts and words."

Tris Imboden, a drummer in Chicago from 1990 until 2018, also took to the social media platform to remember his "dear friend and brother".

He penned: "My dear friend and brother Walt Parazaider passed last night. To say he will be sorely missed is a huge understatement. He, along with Terry Kath and Danny Seraphine, formed the nucleus of what later became the band Chicago.

"Walt, I am beyond honoured to have known you and to have shared so many years, laughs,stages around the world, and so much music with you.

"Sending much love and many prayers to the Parazaider family during this most difficult time."

Walter, the late Terry, Danny, 77, Robert Lamm, 81, Lee Loughnane, 79, and James Pankow, 78, played in the rock band in 1967, originally under the name, The Big Thing, before it became Chicago Transit Authority, then Chicago two years later.

Walter played the saxophone and flute, and performed backing vocals until he retired in 2017.

He contributed to Grammy-winning Chicago's many hits, including If You Leave Me Now, 25 or 6 to 4, and Hard to Say I'm Sorry.

The band - inducted into the Rock + Roll Hall of Fame in 2016 - took to Instagram to inform fans of Walter's death.

Its statement read: "Chicago is heartbroken at the sad news of Walter Parazaider's passing this morning.

"We extend our deepest condolences to his family, friends and countless Chicago fans who are all grieving his loss today.

"A Rock + Roll band with horns was Walt's idea. 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.

"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."