Bob Dylan did a wide spanning interview with Bill Flanagan for his website:
My voice cracking here and there wouldn’t bother me, bum notes or wrong chords would bother me more. On “September of My Years,” I didn’t fix anything. That would be impossible to pull off anyway because we were all in the same room playing together at the same time and there was a lot of leakage into other mics. You only fix things if you overdub the vocals separately and we didn’t do that here. If you mangle a lyric on records like this, you have to go back and start over. It’s a live recording. My voice cracking here or there just might mean it was recorded too early in the day, but it doesn’t hurt the overall effect, it wouldn’t bother me.