George Harrison said Jeff Lynne’s singing voice made him want to try harder on his vocals for his 1987 album, Cloud Nine. However, Lynne might have formed his singing voice on George’s.
For the most part, George’s singing voice was always in top form. Except during his first solo American tour in 1974.
Before his Dark Horse Tour, George did a lot of recording. It exhausted him and wore out his voice.
“That was the problem in 1974, when I toured America,” George explained to Rolling Stone in 1979. “I’d done three albums before I went on the road, and I was still trying to finish my own album as we were rehearsing, and also we’d done this other tour in Europe with these classical Indian musicians. By the time it came to going on the road I was already exhausted.
Source: cheatsheet.com