Jimmy Webb pays tribute to 'extraordinary genius' Glen Campbell

"He's one of the great largely unknown influences on pop music," Webb said.

Webb, who wrote many of Campbell's signature hits and worked with him throughout his life, told ABC News back in May about his relationship and fruitful collaboration with the multi-talented musician.

Reflecting on Campbell's session work, Webb believes his legacy is strong.

Webb admitted that when he and Campbell first met, their opposing political beliefs caused some friction; he was a liberal and Campbell was a conservative. But they were able to put aside their differences.

"We established a place in the middle of our lives where we could work," Webb explained, "and we could give reign to creativity and emotion and reveal deep parts of ourselves as we worked on music."

Webb said he had great respect for Campbell for deciding to tour late in his life, despite struggling with the effects of Alzheimer's disease. Campbell first revealed his diagnosis in 2011, released his album "Ghost on the Canvas" and embarked on a lengthy "goodbye" tour through most of 2012.

"He finished like a champion," Webb said. "And maybe he was the bravest man I've ever known."